ISOLATED NUCLEIC ACIDS, VECTORS AND HOST CELLS ENCODING ErbB3 ANTIBODIES

ABSTRACT

Antibodies are disclosed which bind to ErbB3 protein and further possess any one or more of the following properties: an ability to reduce heregulin-induced formation of an ErbB2-ErbB3 protein complex in a cell which expresses ErbB2 and ErbB3; the ability to increase the binding affinity of heregulin for ErbB3 protein; and the characteristic of reducing heregulin-induced ErbB2 activation in a cell which expresses ErbB2 and ErbB3.

BACKGROUND OF THE INVENTION

This application is a continuation of U.S. application Ser. No.11/051,056 filed Feb. 4, 2005, which is a continuation of U.S.application Ser. No. 09/825,584 filed Apr. 4, 2001, which is adivisional of U.S. application Ser. No. 09/316,981 filed May 24, 1999,which is a continuation of U.S. application Ser. No. 08/827,009 filedMar. 25, 1997 (now U.S. Pat. No. 5,968,511 issued Oct. 19, 1999), whichis a non-provisional application filed under 37 CFR 1.53(b)(1), claimingpriority under USC §119(e) to provisional Application Ser. No.60/046,850 filed Mar. 27, 1996 (now abandoned), which applications areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to antibodies which bind the ErbB3receptor. In particular, it relates to anti-ErbB3 antibodies which,surprisingly, increase the binding affinity of heregulin (HRG) for ErbB3protein and/or reduce HRG-induced formation of an ErbB2-ErbB3 proteincomplex in a cell which expresses both these receptors and/or reduceheregulin-induced ErbB2 activation in such a cell.

DESCRIPTION OF RELATED ART

Transduction of signals that regulate cell growth and differentiation isregulated in part by phosphorylation of various cellular proteins.Protein tyrosine kinases are enzymes that catalyze this process.Receptor protein tyrosine kinases are believed to direct cellular growthvia ligand-stimulated tyrosine phosphorylation of intracellularsubstrates. Growth factor receptor protein tyrosine kinases of the classI subfamily include the 170 kDa epidermal growth factor receptor (EGFR)encoded by the erbB1 gene. erbB1 has been causally implicated in humanmalignancy. In particular, increased expression of this gene has beenobserved in more aggressive carcinomas of the breast, bladder, lung andstomach.

The second member of the class I subfamily, p185^(neu), was originallyidentified as the product of the transforming gene from neuroblastomasof chemically treated rats. The neu gene (also called erbB2 and HER2)encodes a 185 kDa receptor protein tyrosine kinase. Amplification and/oroverexpression of the human HER2 gene correlates with a poor prognosisin breast and ovarian cancers (Slamon et al., Science, 235:177-182(1987); and Slamon et al., Science, 244:707-712 (1989)). Overexpressionof HER2 has also been correlated with other carcinomas includingcarcinomas of the stomach, endometrium, salivary gland, lung, kidney,colon and bladder.

A further related gene, called erbB3 or HER3, has also been described,See U.S. Pat. Nos. 5,183,884 and 5,480,968; Plowman et al., Proc. Natl.Acad. Sci. USA, 87:4905-4909 (1990); Kraus et al., Proc. Natl. Acad.Sci. USA, 86:9193-9197 (1989); EP Pat Appln No 444,961A1; and Kraus etal., Proc. Natl. Acad. Sci. USA, 90:2900-2904 (1993). Kraus et al.,(1989) discovered that markedly elevated levels of erbB3 mRNA werepresent in certain human mammary tumor cell lines indicating that erbB3,like erbB1 and erbB2, may play a role in some human malignancies, Theseresearchers demonstrated that some human mammary tumor cell linesdisplay significant elevation of steady-state ErbB3 tyrosinephosphorylation, further indicating that this receptor may play a rolein human malignancies. Accordingly, diagnostic bioassays utilizingantibodies which bind to ErbB3 are described by Kraus et al., in U.S.Pat. Nos. 5,183,884 and 5,480,968.

The role of erbB3 in cancer has been explored by others. It has beenfound to be overexpressed in breast (Lemoine et al., Br. J. Cancer,66:1116-1121 (1992)), gastrointestinal (Poller et al., J. Pathol.,168:275-280 (1992), Rajkumer et al., J. Pathol., 170:271-278 (1993), andSanidas et al., Int. J. Cancer, 54:935-940 (1993)), and pancreaticcancers (Lemoine et al., J. Pathol., 168:269-273 (1992), and Friess etal., Clinical Cancer Research, 1: 1413-1420 (1995)).

ErbB3 is unique among the ErbB receptor family in that it possesseslittle or no intrinsic tyrosine kinase activity (Guy et al., Proc. Natl.Acad. Sci. USA 91:8132-8136 (1994) and Kim et al. J. Biol. Chem.269:24747-55 (1994)). When ErbB3 is co-expressed with ErbB2, an activesignaling complex is formed and antibodies directed against ErbB2 arecapable of disrupting this complex (Sliwkowski et al., J. Biol. Chem.,269(20):14661-14665 (1994)). Additionally, the affinity of ErbB3 forheregulin (HRG) is increased to a higher affinity state whenco-expressed with ErbB2, See also, Levi et al., Journal of Neuroscience15:1329-1340 (1995); Morrissey et al., Proc. Natl. Acad. Sci. USA92:1431-1435 (1995); and Lewis et al., Cancer Res., 56:1457-1465 (1996)with respect to the ErbB2-ErbB3 protein complex.

Rajkumar et al., British Journal Cancer, 70(3):459-465 (1994), developeda monoclonal antibody against ErbB3 which had an agonistic effect on theanchorage-independent growth of cell lines expressing this receptor.

The class I subfamily of growth factor receptor protein tyrosine kinaseshas been further extended to include the HER4/p180^(erb84) receptor. SeeEP Pat Appln No 599,274; Plowman et al., Proc. Natl. Acad. Sci. USA,90:1746-1750 (1993); and Plowman et al., Nature, 366:473-475 (1993).Plowman et al. found that increased HER4 expression closely correlatedwith certain carcinomas of epithelial origin, including breastadenocarcinomas. Accordingly, diagnostic methods for detection of humanneoplastic conditions (especially breast cancers) which evaluate HER4expression are described in EP Pat Appln No. 599,274.

The quest for an activator of the HER2 oncogene has lead to thediscovery of a family of heregulin polypeptides. These proteins appearto result from alternative splicing of a single gene which was mapped tothe short arm of human chromosome 8 by Lee et al., Genomics, 16:790-791(1993); and Orr-Urtreger et al., Proc. Natl. Acad. Sci. USA,1952:1746-1750 (1993).

Holmes et al. isolated and cloned a family of polypeptide activators forthe HER2 receptor which they termed heregulin-α (HRG-α), heregulin-β1(HRG-β1), heregulin-β2 (HRG-β2), heregulin-β2-like (HRG-β2-like), andheregulin-β3 (HRG-β3). See Holmes et al., Science, 256:1205-1210 (1992);and WO 92/20798. The 45 kDa polypeptide, HRG-α, was purified from theconditioned medium of the MDA-MB-231 human breast cancer cell line.These researchers demonstrated the ability of the purified heregulinpolypeptides to activate tyrosine phosphorylation of the HER2 receptorin MCF-7 breast tumor cells. Furthermore, the mitogenic activity of theheregulin polypeptides on SK-BR-3 cells (which express high levels ofthe HER2 receptor) was illustrated. Like other growth factors whichbelong to the EGF family, soluble HRG polypeptides appear to be derivedfrom a membrane bound precursor (called pro-HRG) which isproteolytically processed to release the 45 kDa soluble form. Thesepro-HRGs lack a N-terminal signal peptide.

While heregulins are substantially identical in the first 213 amino acidresidues, they are classified into two major types, α and β based on twovariant EGF-like domains which differ in their C-terminal portions.Nevertheless, these EGF-like domains are identical in the spacing of sixcysteine residues contained therein. Based on an amino acid sequencecomparison, Holmes et al. found that between the first and sixthcysteines in the EGF-like domain, HRGs were 45% similar toheparin-binding EGF-like growth factor (HB-EGF), 35% identical toamphiregulin (AR), 32% identical to TGF-α, and 27% identical to EGF.

The 44 kDa neu differentiation factor (NDF), which is the rat equivalentof human HRG, was first described by Peles et al., Cell, 69:205-216(1992); and Wen et al., Cell, 69:559-572 (1992). Like the HRGpolypeptides, NDF has an immunoglobulin (Ig) homology domain followed byan EGF-like domain and lacks a N-terminal signal peptide. Subsequently,Wen et al., Mol. Cell. Biol., 14(3): 1909-1919 (1994) carried out“exhaustive cloning” to extend the family of NDFs. This work revealedsix distinct fibroblastic pro-NDFs. Adopting the nomenclature of Holmeset al., the NDFs are classified as either α or β polypeptides based onthe sequences of the EGF-like domains. Isoforms 1 to 4 are characterizedon the basis of the variable juxtamembrane stretch (between the EGF-likedomain and transmembrane domain). Also, isoforms a, b and c aredescribed which have variable length cytoplasmic domains. Theseresearchers conclude that different NDF isoforms are generated byalternative splicing and perform distinct tissue-specific functions.

Falls et al., Cell, 72:801-815 (1993) describe another member of theheregulin family which they call acetylcholine receptor inducingactivity (ARIA) polypeptide. The chicken-derived ARIA polypeptidestimulates synthesis of muscle acetylcholine receptors. See also WO94/08007. ARIA is a β-type heregulin and lacks the entire “glyco” spacer(rich in glycosylation sites) present between the Ig-like domain andEGF-like domain of HRGα, and HRGβ1-β3.

Marchionni et al., Nature, 362:312-318 (1993) identified severalbovine-derived proteins which they call glial growth factors (GGFs).These GGFs share the Ig-like domain and EGF-like domain with the otherheregulin proteins described above, but also have an amino-terminalkringle domain. GGFs generally do not have the complete “glyco” spacerbetween the Ig-like domain and EGF-like domain. Only one of the GGFs,GGFII, possessed a N-terminal signal peptide.

Expression of the ErbB2 family of receptors and heregulin polypeptidesin breast cancer is reviewed in Bacus et al., Pathology Patterns,102(4)(Supp. 1):S13-S24 (1994).

See also, Alimandi et al., Oncogene, 10:1813-1821 (1995); Beerli et al.,Molecular and Cellular Biology, 15:6496-6505 (1995); Karunagaran et al.,EMBO J, 15:254-264 (1996), Wallasch et al., EMBO J, 14:4267-4275 (1995),and Zhang et al., Journal of Biological Chemistry, 271:3884-3890 (1996),in relation to the above receptor family.

SUMMARY OF THE INVENTION

This invention provides antibodies which bind to ErbB3 protein andfurther possess any one or more of the following properties: an abilityto reduce heregulin-induced formation of an ErbB2-ErbB3 protein complexin a cell which expresses ErbB2 and ErbB3; the ability to increase thebinding affinity of heregulin for ErbB3 protein; and the characteristicof reducing heregulin-induced ErbB2 activation in a cell which expressesErbB2 and ErbB3.

The invention also relates to an antibody which binds to ErbB3 proteinand reduces heregulin binding thereto.

Preferred antibodies are monoclonal antibodies which bind to an epitopein the extracellular domain of the ErbB3 receptor. Generally, antibodiesof interest will bind the ErbB3 receptor with an affinity of at leastabout 10 nM, more preferably at least about 1 nM. In certainembodiments, the antibody is immobilized on (e.g. covalently attachedto) a solid phase, e.g., for affinity purification of the receptor orfor diagnostic assays.

The antibodies of the preceding paragraphs may be provided in the formof a composition comprising the antibody and a pharmaceuticallyacceptable carrier or diluent.

The invention also provides: an isolated nucleic acid molecule encodingthe antibody of the preceding paragraphs which may further comprise apromoter operably linked thereto; an expression vector comprising thenucleic acid molecule operably linked to control sequences recognized bya host cell transformed with the vector; a cell line comprising thenucleic acid (e.g. a hybridoma cell line); and a process of using anucleic acid molecule encoding the antibody to effect production of theantibody comprising culturing a cell comprising the nucleic acid and,optionally, recovering the antibody from the cell culture and,preferably, the cell culture medium.

The invention also provides a method for treating a mammal comprisingadministering a therapeutically effective amount of the antibodydescribed herein to the mammal, wherein the mammal has a disorderrequiring treatment with the antibody.

In a further aspect, the invention provides a method for detecting ErbB3in vitro or in vivo comprising contacting the antibody with a cellsuspected of containing ErbB3 and detecting if binding has occurred.Accordingly, the invention provides an assay for detecting a tumorcharacterized by amplified expression of ErbB3 comprising the steps ofexposing a cell to the antibody disclosed herein and determining theextent of binding of the antibody to the cell. Generally the antibodyfor use in such an assay will be labelled. The assay herein may be an invitro assay (such as an ELISA assay) or an in vivo assay. For in vivotumor diagnosis, the antibody is generally conjugated to a radioactiveisotope and administered to a mammal, and the extent of binding of theantibody to tissues in the mammal is observed by external scanning forradioactivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts HRG binding to K562 ErbB3 cells in the presence ofvarious anti-ErbB3 monoclonal antibodies. Purified anti-ErbB3 antibodieswere incubated with a suspension of K562 ErbB3 cells and¹²⁵I-HRGβ1₍₁₇₇₋₂₄₄₎. After approximately 18 hours on ice, cell boundcounts were measured. Counts are shown plotted as a percentage ofbinding in the absence of antibody (control). Non-specific binding wasdetermined using an excess of unlabeled HRGβ1₍₁₇₇₋₂₄₄₎(HRG). Antibodiesagainst ErbB2 protein (2C4) and HSV (5B6) were used as negativecontrols.

FIG. 2 shows the effect of antibody concentration on HRG binding. Adose-response experiment was performed on the 3-8D6 antibody which wasfound to enhance HRG binding. K562 ErbB3 cells were incubated with afixed concentration of ¹²⁵I-HRG and increasing concentrations of the3-8D6 antibody. Data from the experiment is shown plotted as cell boundcounts versus antibody concentration.

FIG. 3 illustrates HRG binding to K562 ErbB3 cells in the presence andabsence of the 3-8D6 antibody or a Fab fragment thereof. Competitiveligand binding experiments were performed in the absence (control) andpresence of 100 nM 3-8D6 or Fab. The data are plotted as bound/total(B/T) versus total HRGβ1₍₁₇₇₋₂₄₄₎.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Definitions

Unless indicated otherwise, the term “ErbB3” when used herein refers tomammalian ErbB3 protein and “erbB3” refers to mammalian erbB3 gene. Thepreferred ErbB3 protein is human ErbB3 protein present in the cellmembrane of a cell. The human erbB3 gene is described in U.S. Pat. No.5,480,968 and Plowman et al., Proc. Natl. Acad. Sci. USA, 87:4905-4909(1990).

The antibody of interest may be one which does not significantlycross-react with other proteins such as those encoded by the erbB1,erbB2 and/or erbB4 genes. In such embodiments, the extent of binding ofthe antibody to these non-ErbB3 proteins (e.g., cell surface binding toendogenous receptor) will be less than 10% as determined by fluorescenceactivated cell sorting (FACS) analysis or radioimmunoprecipitation(RIA). However, sometimes the antibody may be one which does cross-reactwith ErbB4 receptor, and, optionally, does not cross-react with the EGFRand/or ErbB2 receptor, for example.

“Heregulin” (HRG) when used herein refers to a polypeptide whichactivates the ErbB2-ErbB3 protein complex (i.e. induces phosphorylationof tyrosine residues in the ErbB2-ErbB3 complex upon binding thereto).Various heregulin polypeptides encompassed by this term have beendisclosed above. The term includes biologically active fragments and/orvariants of a naturally occurring HRG polypeptide, such as an EGF-likedomain fragment thereof (e.g. HRGβ1₁₇₇₋₂₄₄).

The “ErbB2-ErbB3 protein complex” is a noncovalently associated oligomerof the ErbB2 receptor and the ErbB3 receptor. This complex forms when acell expressing both of these receptors is exposed to HRG. The complexcan be isolated by immunoprecipitation and analyzed by SDS-PAGE asdescribed in the Example below.

The expression “reduces heregulin-induced formation of an ErbB2-ErbB3protein complex in a cell which expresses ErbB2 and ErbB3” refers to theability of the antibody to statistically significantly reduce the numberof ErbB2-ErbB3 protein complexes which form in a cell which has beenexposed to the antibody and HRG relative to an untreated (control) cell.The cell which expresses ErbB2 and ErbB3 can be a naturally occurringcell or cell line (e.g. Caov3 cell) or can be recombinantly produced byintroducing nucleic acid encoding each of these proteins into a hostcell. Preferably, the antibody will reduce formation of this complex byat least 50%, and more preferably at least 70%, as determined byreflectance scanning densitometry of Western blots of the complex (seethe Example below).

The antibody which “reduces heregulin-induced ErbB2 activation in a cellwhich expresses ErbB2 and ErbB3” is one which statisticallysignificantly reduces tyrosine phosphorylation activity of ErbB2 whichoccurs when HRG binds to ErbB3 in the ErbB2-ErbB3 protein complex(present at the surface of a cell which expresses the two receptors)relative to an untreated (control) cell. This can be determined based onphosphotyrosine levels in the ErbB2-ErbB3 complex following exposure ofthe complex to HRG and the antibody of interest. The cell whichexpresses ErbB2 and ErbB3 protein can be a naturally occurring cell orcell line (e.g. Caov3 cell) or can be recombinantly produced. ErbB2activation can be determined by Western blotting followed by probingwith an anti-phosphotyrosine antibody as described in the Example below.Alternatively, the kinase receptor activation assay described in WO95/14930 and Sadick et al., Analytical Biochemistry, 235:207-214 (1996)can be used to quantify ErbB2 activation. Preferably, the antibody willreduce heregulin-induced ErbB2 activation by at least 50%, and morepreferably at least 70%, as determined by reflectance scanningdensitometry of Western blots of the complex probed with ananti-phosphotyrosine antibody (see the Example below).

The antibody may be one which “increases the binding affinity ofheregulin for ErbB3 protein”. This means that, in the presence of theantibody (e.g. 100 nM antibody), the amount of HRG which binds to ErbB3(e.g., endogenous ErbB3 present in a naturally occurring cell or cellline or introduced into a cell by recombinant techniques, see theExample below), relative to control (no antibody), is statisticallysignificantly increased. For example, the amount of HRG which binds tothe K562 cell line transfected with erbB3 as described herein may beincreased in the presence of 100 nM antibody by at least 10% preferablyat least 50% and most preferably at least about 100% (see FIG. 1),relative to control.

The antibody which reduces HRG binding to ErbB3 protein (e.g. ErbB3present in a cell) is one which interferes with the HRG-binding site onErbB3 protein such that it statistically significantly decreases theamount of heregulin which is able to bind to this site on the molecule.Exemplary such antibodies are the 3-2F9, 3-3E9 and 3-6B9 antibodiesdescribed in the Example herein.

The term “antibody” is used in the broadest sense and specificallycovers intact monoclonal antibodies, polyclonal antibodies,multispecific antibodies (e.g. bispecific antibodies) formed from atleast two intact antibodies, and antibody fragments so long as theyexhibit the desired biological activity. The antibody may be an IgM, IgG(e.g. IgG₁, IgG₂, IgG₃ or IgG₄), IgD, IgA or IgE, for example.Preferably however, the antibody is not an IgM antibody.

“Antibody fragments” comprise a portion of an intact antibody, generallythe antigen binding or variable region of the intact antibody. Examplesof antibody fragments include Fab, Fab′, F(ab′)₂, and Fv fragments;diabodies; single-chain antibody molecules; and multispecific antibodiesformed from antibody fragments.

The term “monoclonal antibody” as used herein refers to an antibodyobtained from a population of substantially homogeneous antibodies,i.e., the individual antibodies comprising the population are identicalexcept for possible naturally occurring mutations that may be present inminor amounts. Monoclonal antibodies are highly specific, being directedagainst a single antigenic site. Furthermore, in contrast toconventional (polyclonal) antibody preparations which typically includedifferent antibodies directed against different determinants (epitopes),each monoclonal antibody is directed against a single determinant on theantigen. In addition to their specificity, the monoclonal antibodies areadvantageous in that they are synthesized by the hybridoma culture,uncontaminated by other immunoglobulins. The modifier “monoclonal”indicates the character of the antibody as being obtained from asubstantially homogeneous population of antibodies, and is not to beconstrued as requiring production of the antibody by any particularmethod. For example, the monoclonal antibodies to be used in accordancewith the present invention may be made by the hybridoma method firstdescribed by Kohler et al., Nature, 256:495 (1975), or may be made byrecombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567). The“monoclonal antibodies” may also be isolated from phage antibodylibraries using the techniques described in Clackson et al., Nature,352:624-628 (1991) and Marks et al., J. Mol. Biol., 222:581-597 (1991),for example.

The monoclonal antibodies herein specifically include “chimeric”antibodies (immunoglobulins) in which a portion of the heavy and/orlight chain is identical with or homologous to corresponding sequencesin antibodies derived from a particular species or belonging to aparticular antibody class or subclass, while the remainder of thechain(s) is identical with or homologous to corresponding sequences inantibodies derived from another species or belonging to another antibodyclass or subclass, as well as fragments of such antibodies, so long asthey exhibit the desired biological activity (U.S. Pat. No. 4,816,567;Morrison et al., Proc. Natl. Acad. Sci. USA, 81:6851-6855 (1984)).

“Humanized” forms of non-human (e.g., murine) antibodies are chimericimmunoglobulins, immunoglobulin chains or fragments thereof (such as Fv,Fab, Fab′, F(ab′)₂ or other antigen-binding subsequences of antibodies)which contain minimal sequence derived from non-human immunoglobulin.For the most part, humanized antibodies are human immunoglobulins(recipient antibody) in which residues from acomplementarity-determining region (CDR) of the recipient are replacedby residues from a CDR of a non-human species (donor antibody) such asmouse, rat or rabbit having the desired specificity, affinity, andcapacity. In some instances, Fv framework region (FR) residues of thehuman immunoglobulin are replaced by corresponding non-human residues.Furthermore, humanized antibodies may comprise residues which are foundneither in the recipient antibody nor in the imported CDR or frameworksequences. These modifications are made to further refine and optimizeantibody performance. In general, the humanized antibody will comprisesubstantially all of at least one, and typically two, variable domains,in which all or substantially all of the CDR regions correspond to thoseof a non-human immunoglobulin and all or substantially all of the FRregions are those of a human immunoglobulin sequence. The humanizedantibody optimally also will comprise at least a portion of animmunoglobulin constant region (Fc), typically that of a humanimmunoglobulin. For further details, see Jones et al., Nature,321:522-525 (1986); Reichmann et al., Nature, 332:323-329 (1988); andPresta, Curr. Op. Struct. Biol., 2:593-596 (1992). The humanizedantibody includes a Primatized™ antibody wherein the antigen-bindingregion of the antibody is derived from an antibody produced byimmunizing macaque monkeys with the antigen of interest.

“Single-chain Fv” or “sFv” antibody fragments comprise the V_(H) andV_(L) domains of antibody, wherein these domains are present in a singlepolypeptide chain. Generally, the Fv polypeptide further comprises apolypeptide linker between the V_(H) and V_(L) domains which enables thesFv to form the desired structure for antigen binding. For a review ofsFv see Pluckthun in The Pharmacology of Monoclonal Antibodies, vol.113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315(1994).

The term “diabodies” refers to small antibody fragments with twoantigen-binding sites, which fragments comprise a heavy-chain variabledomain (V_(H)) connected to a light-chain variable domain (V_(L)) in thesame polypeptide chain (V_(H)-V_(L)). By using a linker that is tooshort to allow pairing between the two domains on the same chain, thedomains are forced to pair with the complementary domains of anotherchain and create two antigen-binding sites. Diabodies are described morefully in, for example, EP 404,097; WO 93/11161; and Hollinger et al.,Proc. Natl. Acad. Sci. USA, 90:6444-6448 (1993).

An “isolated” antibody is one which has been identified and separatedand/or recovered from a component of its natural environment.Contaminant components of its natural environment are materials whichwould interfere with diagnostic or therapeutic uses for the antibody,and may include enzymes, hormones, and other proteinaceous ornonproteinaceous solutes. In preferred embodiments, the antibody will bepurified (1) to greater than 95% by weight of antibody as determined bythe Lowry method, and most preferably more than 99% by weight, (2) to adegree sufficient to obtain at least 15 residues of N-terminal orinternal amino acid sequence by use of a spinning cup sequenator, or (3)to homogeneity by SDS-PAGE under reducing or nonreducing conditionsusing Coomassie blue or, preferably, silver stain. Isolated antibodyincludes the antibody in situ within recombinant cells since at leastone component of the antibody's natural environment will not be present.Ordinarily, however, isolated antibody will be prepared by at least onepurification step.

As used herein, the term “salvage receptor binding epitope” refers to anepitope of the Fc region of an IgG molecule (e.g., IgG₁, IgG₂, IgG₃, orIgG₄) that is responsible for increasing the in vivo serum half-life ofthe IgG molecule.

“Treatment” refers to both therapeutic treatment and prophylactic orpreventative measures. Those in need of treatment include those alreadywith the disorder as well as those in which the disorder is to beprevented.

“Mammal” for purposes of treatment refers to any animal classified as amammal, including humans, domestic and farm animals, and zoo, sports, orpet animals, such as dogs, horses, cats, cows, etc. Preferably, themammal is human.

A “disorder” is any condition that would benefit from treatment with theanti-ErbB3 antibody. This includes chronic and acute disorders ordiseases including those pathological conditions which predispose themammal to the disorder in question. Generally, the disorder will be onein which excessive activation of the ErbB2-ErbB3 protein complex byheregulin is occurring. Non-limiting examples of disorders to be treatedherein include benign and malignant tumors; leukemias and lymphoidmalignancies; neuronal, glial, astrocytal, hypothalamic and otherglandular, macrophagal, epithelial, stromal and blastocoelic disorders;and inflammatory, angiogenic and immunologic disorders.

The terms “cancer” and “cancerous” refer to or describe thephysiological condition in mammals that is typically characterized byunregulated cell growth. Examples of cancer include but are not limitedto, carcinoma, lymphoma, blastoma, sarcoma, and leukemia. Moreparticular examples of such cancers include squamous cell cancer,small-cell lung cancer, non-small cell lung cancer, gastrointestinalcancer, pancreatic cancer, glioblastoma, cervical cancer, ovariancancer, liver cancer, bladder cancer, hepatoma, breast cancer, coloncancer, colorectal cancer, endometrial carcinoma, salivary glandcarcinoma, kidney cancer, renal cancer, prostate cancer, vulval cancer,thyroid cancer, hepatic carcinoma and various types of head and neckcancer.

The term “cytotoxic agent” as used herein refers to a substance thatinhibits or prevents the function of cells and/or causes destruction ofcells. The term is intended to include radioactive isotopes (e.g. 1, Y,Pr), chemotherapeutic agents, and toxins such as enzymatically activetoxins of bacterial, fungal, plant or animal origin, or fragmentsthereof.

A “chemotherapeutic agent” is a chemical compound useful in thetreatment of cancer. Examples of chemotherapeutic agents includeAdriamycin, Doxorubicin, 5-Fluorouracil, Cytosine arabinoside (“Ara-C”),Cyclophosphamide, Thiotepa, Busulfan, Cytoxin, Taxol, Methotrexate,Cisplatin, Melphalan, Vinblastine, Bleomycin, Etoposide, Ifosfamide,Mitomycin C, Mitoxantrone, Vincreistine, Vinorelbine, Carboplatin,Teniposide, Daunomycin, Carminomycin, Aminopterin, Dactinomycin,Mitomycins, Esperamicins (see U.S. Pat. No. 4,675,187), Melphalan andother related nitrogen mustards.

The term “cytokine” is a generic term for proteins released by one cellpopulation which act on another cell as intercellular mediators.Examples of such cytokines are lymphokines, monokines, and traditionalpolypeptide hormones. Included among the cytokines are growth hormonesuch as human growth hormone, N-methionyl human growth hormone, andbovine growth hormone; parathyroid hormone; thyroxine; insulin;proinsulin; relaxin; prorelaxin; glycoprotein hormones such as folliclestimulating hormone (FSH), thyroid stimulating hormone (TSH), andluteinizing hormone (LH); hepatic growth factor; fibroblast growthfactor; prolactin; placental lactogen; tumor necrosis factor-α and -β;mullerian-inhibiting substance; mouse gonadotropin-associated peptide;inhibin; activin; vascular endothelial growth factor; integrin;thrombopoietin (TPO); nerve growth factors such as NGF-β;platelet-growth factor; transforming growth factors (TGFs) such as TGF-αand TGF-β; insulin-like growth factor-I and -II; erythropoietin (EPO);osteoinductive factors; interferons such as interferon-α, -β, and -γ;colony stimulating factors (CSFs) such as macrophage-CSF (M-CSF);granulocyte-macrophage-CSF (GM-CSF); and granulocyte-CSF (G-CSF);interleukins (ILs) such as IL-1, IL-1α, IL-2, IL-3, IL-4, IL-5, IL-6,IL-7, IL-8, IL-9, IL-11, IL-12; a tumor necrosis factor such as TNF-α orTNF-β; and other polypeptide factors including LIF and kit ligand (KL).As used herein, the term cytokine includes proteins from natural sourcesor from recombinant cell culture and biologically active equivalents ofthe native sequence cytokines.

The term “prodrug” as used in this application refers to a precursor orderivative form of a pharmaceutically active substance that is lesscytotoxic to tumor cells compared to the parent drug and is capable ofbeing enzymatically activated or converted into the more active parentform, See, e.g., Wilman, “Prodrugs in Cancer Chemotherapy” BiochemicalSociety Transactions, 14, pp. 375-382, 615th Meeting Belfast (1986) andStella et al., “Prodrugs: A Chemical Approach to Targeted DrugDelivery,” Directed Drug Delivery, Borchardt et al., (ed.), pp. 247-267,Humana Press (1985). The prodrugs of this invention include, but are notlimited to, phosphate-containing prodrugs, thiophosphate-containingprodrugs, sulfate-containing prodrugs, peptide-containing prodrugs,D-amino acid-modified prodrugs, glycosylated prodrugs,β-lactam-containing prodrugs, optionally substitutedphenoxyacetamide-containing prodrugs or optionally substitutedphenylacetamide-containing prodrugs, 5-fluorocytosine and other5-fluorouridine prodrugs which can be converted into the more activecytotoxic free drug. Examples of cytotoxic drugs that can be derivatizedinto a prodrug form for use in this invention include, but are notlimited to, those chemotherapeutic agents described above.

The word “label” when used herein refers to a detectable compound orcomposition which is conjugated directly or indirectly to the antibody.The label may be detectable by itself (e.g. radioisotope labels orfluorescent labels) or, in the case of an enzymatic label, may catalyzechemical alteration of a substrate compound or composition which isdetectable.

By “solid phase” is meant a non-aqueous matrix to which the antibody ofthe present invention can adhere. Examples of solid phases encompassedherein include those formed partially or entirely of glass (e.g.,controlled pore glass), polysaccharides (e.g., agarose),polyacrylamides, polystyrene, polyvinyl alcohol and silicones. Incertain embodiments, depending on the context, the solid phase cancomprise the well of an assay plate, in others it is a purificationcolumn (e.g., an affinity chromatography column). This term alsoincludes a discontinuous solid phase of discrete particles, such asthose described in U.S. Pat. No. 4,275,149.

A “liposome” is a small vesicle composed of various types of lipids,phospholipids and/or surfactant which is useful for delivery of a drug(such as the anti-ErbB3 antibodies disclosed herein and, optionally, achemotherapeutic agent) to a mammal. The components of the liposome arecommonly arranged in a bilayer formation, similar to the lipidarrangement of biological membranes.

An “isolated” nucleic acid molecule is a nucleic acid molecule that isidentified and separated from at least one contaminant nucleic acidmolecule with which it is ordinarily associated in the natural source ofthe antibody nucleic acid. An isolated nucleic acid molecule is otherthan in the form or setting in which it is found in nature. Isolatednucleic acid molecules therefore are distinguished from the nucleic acidmolecule as it exists in natural cells. However, an isolated nucleicacid molecule includes a nucleic acid molecule contained in cells thatordinarily express the antibody where, for example, the nucleic acidmolecule is in a chromosomal location different from that of naturalcells.

The expression “control sequences” refers to DNA sequences necessary forthe expression of an operably linked coding sequence in a particularhost organism. The control sequences that are suitable for prokaryotes,for example, include a promoter, optionally an operator sequence, and aribosome binding site. Eukaryotic cells are known to utilize promoters,polyadenylation signals, and enhancers.

Nucleic acid is “operably linked” when it is placed into a functionalrelationship with another nucleic acid sequence. For example, DNA for apresequence or secretory leader is operably linked to DNA for apolypeptide if it is expressed as a preprotein that participates in thesecretion of the polypeptide; a promoter or enhancer is operably linkedto a coding sequence if it affects the transcription of the sequence, ora ribosome binding site is operably linked to a coding sequence if it ispositioned so as to facilitate translation. Generally, “operably linked”means that the DNA sequences being linked are contiguous, and, in thecase of a secretory leader, contiguous and in reading phase. However,enhancers do not have to be contiguous. Linking is accomplished byligation at convenient restriction sites. If such sites do not exist,the synthetic oligonucleotide adaptors or linkers are used in accordancewith conventional practice.

As used herein, the expressions “cell,” “cell line,” and “cell culture”are used interchangeably and all such designations include progeny.Thus, the words “transformants” and “transformed cells” include theprimary subject cell and cultures derived therefrom without regard forthe number of transfers. It is also understood that all progeny may notbe precisely identical in DNA content, due to deliberate or inadvertentmutations. Mutant progeny that have the same function or biologicalactivity as screened for in the originally transformed cell areincluded. Where distinct designations are intended, it will be clearfrom the context.

II. Modes for Carrying Out the Invention

A. Antibody Preparation

A description follows as to exemplary techniques for the production ofthe claimed antibodies.

(i) Polyclonal Antibodies

Polyclonal antibodies are generally raised in animals by multiplesubcutaneous (sc) or intraperitoneal (ip) injections of the relevantantigen and an adjuvant. It may be useful to conjugate the relevantantigen to a protein that is immunogenic in the species to be immunized,e.g., keyhole limpet hemocyanin, serum albumin, bovine thyroglobulin, orsoybean trypsin inhibitor using a bifunctional or derivatizing agent,for example, maleimidobenzoyl sulfosuccinimide ester (conjugationthrough cysteine residues), N-hydroxysuccinimide (through lysineresidues), glutaraldehyde, succinic anhydride, SOCl₂, or R¹N═C═NR, whereR and R¹ are different alkyl groups.

Animals are immunized against the antigen, immunogenic conjugates, orderivatives by combining, e.g., 100 μg or 5 μg of the protein orconjugate (for rabbits or mice, respectively) with 3 volumes of Freund'scomplete adjuvant and injecting the solution intradermally at multiplesites. One month later the animals are boosted with ⅕ to 1/10 theoriginal amount of peptide or conjugate in Freund's complete adjuvant bysubcutaneous injection at multiple sites. Seven to 14 days later theanimals are bled and the serum is assayed for antibody titer. Animalsare boosted until the titer plateaus. Preferably, the animal is boostedwith the conjugate of the same antigen, but conjugated to a differentprotein and/or through a different cross-linking reagent. Conjugatesalso can be made in recombinant cell culture as protein fusions. Also,aggregating agents such as alum are suitably used to enhance the immuneresponse.

(ii) Monoclonal Antibodies

Monoclonal antibodies are obtained from a population of substantiallyhomogeneous antibodies, i.e., the individual antibodies comprising thepopulation are identical except for possible naturally occurringmutations that may be present in minor amounts. Thus, the modifier“monoclonal” indicates the character of the antibody as not being amixture of discrete antibodies.

For example, the monoclonal antibodies may be made using the hybridomamethod first described by Kohler et al., Nature, 256:495 (1975), or maybe made by recombinant DNA methods (U.S. Pat. No. 4,816,567).

In the hybridoma method, a mouse or other appropriate host animal, suchas a hamster, is immunized as hereinabove described to elicitlymphocytes that produce or are capable of producing antibodies thatwill specifically bind to the protein used for immunization,Alternatively, lymphocytes may be immunized in vitro. Lymphocytes thenare fused with myeloma cells using a suitable fusing agent, such aspolyethylene glycol, to form a hybridoma cell (Goding, MonoclonalAntibodies: Principles and Practice, pp. 59-103 (Academic Press, 1986)).

The hybridoma cells thus prepared are seeded and grown in a suitableculture medium that preferably contains one or more substances thatinhibit the growth or survival of the unfused, parental myeloma cells,For example, if the parental myeloma cells lack the enzyme hypoxanthineguanine phosphoribosyl transferase (HGPRT or HPRT), the culture mediumfor the hybridomas typically will include hypoxanthine, aminopterin, andthymidine (HAT medium), which substances prevent the growth ofHGPRT-deficient cells.

Preferred myeloma cells are those that fuse efficiently, support stablehigh-level production of antibody by the selected antibody-producingcells, and are sensitive to a medium such as HAT medium. Among these,preferred myeloma cell lines are murine myeloma lines, such as thosederived from MOPC-21 and MPC-11 mouse tumors available from the SalkInstitute Cell Distribution Center, San Diego, Calif. USA, and SP-2 orX63-Ag8-653 cells available from the American Type Culture Collection,Rockville, Md. USA. Human myeloma and mouse-human heteromyeloma celllines also have been described for the production of human monoclonalantibodies (Kozbor, J. Immunol., 133:3001 (1984), Brodeur et al.,Monoclonal Antibody Production Techniques and Applications, pp. 51-63(Marcel Dekker, Inc., New York, 1987)).

Culture medium in which hybridoma cells are growing is assayed forproduction of monoclonal antibodies directed against the antigen.Preferably, the binding specificity of monoclonal antibodies produced byhybridoma cells is determined by immunoprecipitation or by an in vitrobinding assay, such as radioimmunoassay (RIA) or enzyme-linkedimmunoabsorbent assay (ELISA).

The binding affinity of the monoclonal antibody can, for example, bedetermined by the Scatchard analysis of Munson et al., Anal. Biochem.,107:220(1980).

After hybridoma cells are identified that produce antibodies of thedesired specificity, affinity, and/or activity, the clones may besubcloned by limiting dilution procedures and grown by standard methods(Goding, Monoclonal Antibodies: Principles and Practice, pp. 59-103(Academic Press, 1986)). Suitable culture media for this purposeinclude, for example, D-MEM or RPMI-1640 medium. In addition, thehybridoma cells may be grown in vivo as ascites tumors in an animal.

The monoclonal antibodies secreted by the subclones are suitablyseparated from the culture medium, ascites fluid, or serum byconventional immunoglobulin purification procedures such as, forexample, protein A-Sepharose, hydroxylapatite chromatography, gelelectrophoresis, dialysis, or affinity chromatography.

DNA encoding the monoclonal antibodies is readily isolated and sequencedusing conventional procedures (e.g., by using oligonucleotide probesthat are capable of binding specifically to genes encoding the heavy andlight chains of murine antibodies). The hybridoma cells serve as apreferred source of such DNA. Once isolated, the DNA may be placed intoexpression vectors, which are then transfected into host cells such asE. coli/cells, simian COS cells, Chinese hamster ovary (CHO) cells, ormyeloma cells that do not otherwise produce immunoglobulin protein, toobtain the synthesis of monoclonal antibodies in the recombinant hostcells. Review articles on recombinant expression in bacteria of DNAencoding the antibody include Skerra et al., Curr. Opinion in Immunol.,5:256-262 (1993) and Plückthun, Immunol. Revs., 130:151-188 (1992).

In a further embodiment, antibodies or antibody fragments can beisolated from antibody phage libraries generated using the techniquesdescribed in McCafferty et al., Nature, 348:552-554 (1990). Clackson etal., Nature, 352:624-628 (1991) and Marks et al., J. Mol. Biol.,222:581-597 (1991) describe the isolation of murine and humanantibodies, respectively, using phage libraries. Subsequent publicationsdescribe the production of high affinity (nM range) human antibodies bychain shuffling (Marks et al., Bio/Technology, 10:779-783 (1992)), aswell as combinatorial infection and in vivo recombination as a strategyfor constructing very large phage libraries (Waterhouse et al., Nuc.Acids. Res., 21:2265-2266 (1993)). Thus, these techniques are viablealternatives to traditional monoclonal antibody hybridoma techniques forisolation of monoclonal antibodies.

The DNA also may be modified, for example, by substituting the codingsequence for human heavy- and light-chain constant domains in place ofthe homologous murine sequences (U.S. Pat. No. 4,816,567; Morrison, etal., Proc. Natl Acad. Sci. USA, 81:6851 (1984)), or by covalentlyjoining to the immunoglobulin coding sequence all or part of the codingsequence for a non-immunoglobulin polypeptide.

Typically such non-immunoglobulin polypeptides are substituted for theconstant domains of an antibody, or they are substituted for thevariable domains of one antigen-combining site of an antibody to createa chimeric bivalent antibody comprising one antigen-combining sitehaving specificity for an antigen and another antigen-combining sitehaving specificity for a different antigen.

(iii) Humanized and Human Antibodies

Methods for humanizing non-human antibodies are well known in the art.Generally, a humanized antibody has one or more amino acid residuesintroduced into it from a source which is non-human. These non-humanamino acid residues are often referred to as “import” residues, whichare typically taken from an “import” variable domain. Humanization canbe essentially performed following the method of Winter and co-workers(Jones et al., Nature, 321:522-525 (1986); Riechmann et al., Nature,332:323-327 (1988); Verhoeyen et al., Science, 239:1534-1536 (1988)), bysubstituting rodent CDRs or CDR sequences for the correspondingsequences of a human antibody. Accordingly, such “humanized” antibodiesare chimeric antibodies (U.S. Pat. No. 4,816,567) wherein substantiallyless than an intact human variable domain has been substituted by thecorresponding sequence from a non-human species. In practice, humanizedantibodies are typically human antibodies in which some CDR residues andpossibly some FR residues are substituted by residues from analogoussites in rodent antibodies.

The choice of human variable domains, both light and heavy, to be usedin making the humanized antibodies is very important to reduceantigenicity. According to the so-called “best-fit” method, the sequenceof the variable domain of a rodent antibody is screened against theentire library of known human variable-domain sequences. The humansequence which is closest to that of the rodent is then accepted as thehuman framework (FR) for the humanized antibody (Sims et al., J.Immunol., 151:2296 (1993); Chothia et al., J. Mol. Biol., 196:901(1987)). Another method uses a particular framework derived from theconsensus sequence of all human antibodies of a particular subgroup oflight or heavy chains. The same framework may be used for severaldifferent humanized antibodies (Carter et al., Proc. Natl. Acad. Sci.USA, 89:4285 (1992); Presta et al., J. Immunol., 151:2623 (1993)).

It is further important that antibodies be humanized with retention ofhigh affinity for the antigen and other favorable biological properties.To achieve this goal, according to a preferred method, humanizedantibodies are prepared by a process of analysis of the parentalsequences and various conceptual humanized products usingthree-dimensional models of the parental and humanized sequences.Three-dimensional immunoglobulin models are commonly available and arefamiliar to those skilled in the art. Computer programs are availablewhich illustrate and display probable three-dimensional conformationalstructures of selected candidate immunoglobulin sequences. Inspection ofthese displays permits analysis of the likely role of the residues inthe functioning of the candidate immunoglobulin sequence, i.e., theanalysis of residues that influence the ability of the candidateimmunoglobulin to bind its antigen. In this way, FR residues can beselected and combined from the recipient and import sequences so thatthe desired antibody characteristic, such as increased affinity for thetarget antigen(s), is achieved. In general, the CDR residues aredirectly and most substantially involved in influencing antigen binding.

Alternatively, it is now possible to produce transgenic animals (e.g.,mice) that are capable, upon immunization, of producing a fullrepertoire of human antibodies in the absence of endogenousimmunoglobulin production. For example, it has been described that thehomozygous deletion of the antibody heavy-chain joining region (J_(H))gene in chimeric and germ-line mutant mice results in completeinhibition of endogenous antibody production. Transfer of the humangerm-line immunoglobulin gene array in such germ-line mutant mice willresult in the production of human antibodies upon antigen challenge.See, e.g., Jakobovits et al., Proc. Natl. Acad. Sc. USA, 90:2551 (1993);Jakobovits et al., Nature, 362:255-258 (1993); Bruggermann et al., Yearin Immuno., 7:33 (1993). Human antibodies can also be derived fromphage-display libraries (Hoogenboom et al., J. Mol. Biol., 227:381(1991); Marks et al., J. Mol. Biol., 222:581-597 (1991)).

(iv) Antibody Fragments

Various techniques have been developed for the production of antibodyfragments. Traditionally, these fragments were derived via proteolyticdigestion of intact antibodies (see, e.g., Morimoto et al., Journal ofBiochemical and Biophysical Methods 24:107-117 (1992) and Brennan etal., Science, 229:81 (1985)), However, these fragments can now beproduced directly by recombinant host cells. For example, the antibodyfragments can be isolated from the antibody phage libraries discussedabove. Alternatively, Fab′-SH fragments can be directly recovered fromE. coli and chemically coupled to form F(ab′)₂ fragments (Carter et al.,Bio/Technology 10:163-167 (1992)). According to another approach,F(ab′)₂ fragments can be isolated directly from recombinant host cellculture. Other techniques for the production of antibody fragments willbe apparent to the skilled practitioner.

(v) Bispecific Antibodies

Bispecific antibodies are antibodies that have binding specificities forat least two different epitopes. Exemplary bispecific antibodies maybind to two different epitopes of the ErbB3 protein. Other suchantibodies may combine an ErbB3 binding site with binding site(s) forEGFR, ErbB2 and/or ErbB4. Alternatively, an anti-ErbB3 arm may becombined with an arm which binds to a triggering molecule on a leukocytesuch as a T-cell receptor molecule (e.g. CD2 or CD3), or Fc receptorsfor IgG (FcyR), such as FcyRI (CD64), FcyRII (CD32) and FcyRIII (CD16)so as to focus cellular defense mechanisms to the ErbB3-expressing cell.Bispecific antibodies may also be used to localize cytotoxic agents tocells which express ErbB3. These antibodies possess an ErbB3-binding armand an arm which binds the cytotoxic agent (e.g. saporin,anti-interferon-α, vinca alkaloid, ricin A chain, methotrexate orradioactive isotope hapten). Bispecific antibodies can be prepared asfull length antibodies or antibody fragments (e.g. F(ab′)₂ bispecificantibodies).

Methods for making bispecific antibodies are known in the art.Traditional production of full length bispecific antibodies is based onthe coexpression of two immunoglobulin heavy chain-light chain pairs,where the two chains have different specificities (Millstein et al.,Nature, 305:537-539 (1983)). Because of the random assortment ofimmunoglobulin heavy and light chains, these hybridomas (quadromas)produce a potential mixture of 10 different antibody molecules, of whichonly one has the correct bispecific structure. Purification of thecorrect molecule, which is usually done by affinity chromatographysteps, is rather cumbersome, and the product yields are low. Similarprocedures are disclosed in WO 93/08829, and in Traunecker et al., EMBOJ., 10:3655-3659 (1991).

According to a different approach, antibody variable domains with thedesired binding specificities (antibody-antigen combining sites) arefused to immunoglobulin constant domain sequences. The fusion preferablyis with an immunoglobulin heavy chain constant domain, comprising atleast part of the hinge, CH2, and CH3 regions. It is preferred to havethe first heavy-chain constant region (CH1) containing the sitenecessary for light chain binding, present in at least one of thefusions. DNAs encoding the immunoglobulin heavy chain fusions and, ifdesired, the immunoglobulin light chain, are inserted into separateexpression vectors, and are co-transfected into a suitable hostorganism. This provides for great flexibility in adjusting the mutualproportions of the three polypeptide fragments in embodiments whenunequal ratios of the three polypeptide chains used in the constructionprovide the optimum yields. It is, however, possible to insert thecoding sequences for two or all three polypeptide chains in oneexpression vector when the expression of at least two polypeptide chainsin equal ratios results in high yields or when the ratios are of noparticular significance.

In a preferred embodiment of this approach, the bispecific antibodiesare composed of a hybrid immunoglobulin heavy chain with a first bindingspecificity in one arm, and a hybrid immunoglobulin heavy chain-lightchain pair (providing a second binding specificity) in the other arm. Itwas found that this asymmetric structure facilitates the separation ofthe desired bispecific compound from unwanted immunoglobulin chaincombinations, as the presence of an immunoglobulin light chain in onlyone half of the bispecific molecule provides for a facile way ofseparation. This approach is disclosed in WO 94/04690. For furtherdetails of generating bispecific antibodies see, for example, Suresh etal., Methods in Enzymology, 121:210 (1986).

According to another approach, the interface between a pair of antibodymolecules can be engineered to maximize the percentage of heterodimerswhich are recovered from recombinant cell culture. The preferredinterface comprises at least a part of the C_(H)3 domain of an antibodyconstant domain. In this method, one or more small amino acid sidechains from the interface of the first antibody molecule are replacedwith larger side chains (e.g. tyrosine or tryptophan). Compensatory“cavities” of identical or similar size to the large side chain(s) arecreated on the interface of the second antibody molecule by replacinglarge amino acid side chains with smaller ones (e.g. alanine orthreonine). This provides a mechanism for increasing the yield of theheterodimer over other unwanted end-products such as homodimers.

Bispecific antibodies include cross-linked or “heteroconjugate”antibodies. For example, one of the antibodies in the heteroconjugatecan be coupled to avidin, the other to biotin. Such antibodies have, forexample, been proposed to target immune system cells to unwanted cells(U.S. Pat. No. 4,676,980), and for treatment of HIV infection (WO91/00360, WO 92/200373, and EP 03089). Heteroconjugate antibodies may bemade using any convenient cross-linking methods. Suitable cross-linkingagents are well known in the art, and are disclosed in U.S. Pat. No.4,676,980, along with a number of cross-linking techniques.

Techniques for generating bispecific antibodies from antibody fragmentshave also been described in the literature. For example, bispecificantibodies can be prepared using chemical linkage. Brennan et al.,Science, 229: 81 (1985) describe a procedure wherein intact antibodiesare proteolytically cleaved to generate F(ab′)₂ fragments. Thesefragments are reduced in the presence of the dithiol complexing agentsodium arsenite to stabilize vicinal dithiols and prevent intermoleculardisulfide formation, The Fab′ fragments generated are then converted tothionitrobenzoate (TNB) derivatives. One of the Fab′-TNB derivatives isthen reconverted to the Fab′-thiol by reduction with mercaptoethylamineand is mixed with an equimolar amount of the other Fab′-TNB derivativeto form the bispecific antibody. The bispecific antibodies produced canbe used as agents for the selective immobilization of enzymes.

Recent progress has facilitated the direct recovery of Fab′-SH fragmentsfrom E. coli, which can be chemically coupled to form bispecificantibodies. Shalaby et al., J. Exp. Med., 175: 217-225 (1992) describethe production of a fully humanized bispecific antibody F(ab′)₂molecule. Each Fab′ fragment was separately secreted from E. coli andsubjected to directed chemical coupling in vitro to form the bispecificantibody. The bispecific antibody thus formed was able to bind to cellsoverexpressing the HER2 receptor and normal human T cells, as well astrigger the lytic activity of human cytotoxic lymphocytes against humanbreast tumor targets.

Various techniques for making and isolating bispecific antibodyfragments directly from recombinant cell culture have also beendescribed. For example, bispecific antibodies have been produced usingleucine zippers. Kostelny et al., J. Immunol., 148(5):1547-1553 (1992).The leucine zipper peptides from the Fos and Jun proteins were linked tothe Fab′ portions of two different antibodies by gene fusion. Theantibody homodimers were reduced at the hinge region to form monomersand then re-oxidized to form the antibody heterodimers. This method canalso be utilized for the production of antibody homodimers. The“diabody” technology described by Hollinger et al., Proc. Natl. Acad.Sci. USA, 90:6444-6448 (1993) has provided an alternative mechanism formaking bispecific antibody fragments. The fragments comprise aheavy-chain variable domain (V_(H)) connected to a light-chain variabledomain (V_(L)) by a linker which is too short to allow pairing betweenthe two domains on the same chain. Accordingly, the V_(H) and V_(L)domains of one fragment are forced to pair with the complementary V_(L)and V_(H) domains of another fragment, thereby forming twoantigen-binding sites. Another strategy for making bispecific antibodyfragments by the use of single-chain Fv (sFv) dimers has also beenreported. See Gruber et al., J. Immunol., 152:5368 (1994).

Antibodies with more than two valencies are contemplated. For example,trispecific antibodies can be prepared. Tutt et al. J. Immunol. 147: 60(1991).

(vi) Screening for Antibodies with the Desired Properties

Techniques for generating antibodies have been described above. Thoseantibodies having the characteristics described herein are selected.

To select for antibodies which reduce HRG-induced formation of theErbB2-ErbB3 protein complex, cells which express both these receptors(e.g. Caov3 cells) can be pre-incubated with buffer (control) orantibody, then treated with HRG or control buffer. The cells are thenlysed and the crude lysates can be centrifuged to remove insolublematerial. Supernatants may be incubated with an antibody specific forErbB2 covalently coupled to a solid phase. Following washing, theimmunoprecipitates may be separated by SDS-PAGE. Western blots of thegels are then probed with anti-ErbB3 antibody. After visualization, theblots may be stripped and re-probed with an anti-ErbB2 antibody.Reflectance scanning densitometry of the gel can be performed in orderto quantify the effect of the antibody in question on HRG-inducedformation of the complex. Those antibodies which reduce formation of theErbB2-ErbB3 complex relative to control (untreated cells) can beselected. See the Example below.

To select for those antibodies which reduce HRG-induced ErbB2 activationin a cell which expresses the ErbB2 and ErbB3 receptor, the cells can bepre-incubated with buffer (control) or antibody, then treated with HRGor control buffer. The cells are then lysed and the crude lysates can becentrifuged to remove insoluble material. ErbB2 activation can bedetermined by Western blotting followed by probing with ananti-phosphotyrosine antibody as described in the Example below. ErbB2activation can be quantified via reflectance scanning densitometry ofthe gel, for example. Alternatively, the kinase receptor activationassay described in WO 95/14930 and Sadick et al., AnalyticalBiochemistry, 235:207-214 (1996) can be used to determine ErbB2activation.

The effect of the antibody on HRG binding to ErbB3 can be determined byincubating cells which express this receptor (e.g. 4E9H3 cellstransfected to express ErbB3) with radiolabelled HRG (e.g. the EGF-likedomain thereof), in the absence (control) or presence of the anti-ErbB3antibody, as described in the Example below, for example. Thoseantibodies which increase the binding affinity of HRG for the ErbB3receptor can be selected for further development. Where the antibody ofchoice is one which blocks binding of HRG to ErbB3, those antibodieswhich do so in this assay can be identified.

To screen for antibodies which bind to the epitope on ErbB3 bound by anantibody of interest (e.g., those which block binding of the 3-8B8antibody to ErbB3), a routine cross-blocking assay such as thatdescribed in Antibodies, A Laboratory Manual, Cold Spring HarborLaboratory, Ed Harlow and David Lane (1988), can be performed.

(vii) Effector Function Engineering

It may be desirable to modify the antibody of the invention with respectto effector function, so as to enhance the effectiveness of the antibodyin treating cancer, for example. For example cysteine residue(s) may beintroduced in the Fc region, thereby allowing interchain disulfide bondformation in this region. The homodimeric antibody thus generated mayhave improved internalization capability and/or increasedcomplement-mediated cell killing and antibody-dependent cellularcytotoxicity (ADCC). See Caron et al., J. Exp Med. 176:1191-1195 (1992)and Shopes, B. J. Immunol. 148:2918-2922 (1992). Homodimeric antibodieswith enhanced anti-tumor activity may also be prepared usingheterobifunctional cross-linkers as described in Wolff et al. CancerResearch 53:2560-2565 (1993). Alternatively, an antibody can beengineered which has dual Fc regions and may thereby have enhancedcomplement lysis and ADCC capabilities. See Stevenson et al. Anti-CancerDrug Design 3:219-230 (1989).

(viii) Immunoconjugates

The invention also pertains to immunoconjugates comprising the antibodydescribed herein conjugated to a cytotoxic agent such as achemotherapeutic agent, toxin (e.g. an enzymatically active toxin ofbacterial, fungal, plant or animal origin, or fragments thereof), or aradioactive isotope (i.e., a radioconjugate).

Chemotherapeutic agents useful in the generation of suchimmunoconjugates have been described above. Enzymatically active toxinsand fragments thereof which can be used include diphtheria A chain,nonbinding active fragments of diphtheria toxin, exotoxin A chain (fromPseudomonas aeruginosa), ricin A chain, abrin A chain, modeccin A chain,alpha-sarcin, Aleurites fordii proteins, dianthin proteins, Phytolacaamericana proteins (PAPI, PAPII, and PAP-S), momordica charantiainhibitor, curcin, crotin, sapaonaria officinalis inhibitor, gelonin,mitogellin, restrictocin, phenomycin, enomycin and the tricothecenes. Avariety of radionuclides are available for the production ofradioconjugated anti-ErbB3 antibodies. Examples include ²¹²Bl, ¹³¹I,¹³¹In, ⁹⁰Y and ¹⁸⁶Re.

Conjugates of the antibody and cytotoxic agent are made using a varietyof bifunctional protein coupling agents such asN-succinimidyl-3-(2-pyridyldithiol) propionate (SPDP), iminothiolane(IT), bifunctional derivatives of imidoesters (such as dimethyladipimidate HCL), active esters (such as disuccinimidyl suberate),aldehydes (such as glutareldehyde), bis-azido compounds (such asbis(p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (such asbis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (such astolyene 2,6-diisocyanate), and bis-active fluorine compounds (such as1,5-difluoro-2,4-dinitrobenzene). For example, a ricin immunotoxin canbe prepared as described in Vitetta et al. Science 238: 1098 (1987).Carbon-14-labeled 1-isothiocyanatobenzyl-3-methyldiethylenetriaminepentaacetic acid (MX-DTPA) is an exemplary chelating agent forconjugation of radionucleotide to the antibody. See WO94/11026.

In another embodiment, the antibody may be conjugated to a “receptor”(such streptavidin) for utilization in tumor pretargeting wherein theantibody-receptor conjugate is administered to the patient, followed byremoval of unbound conjugate from the circulation using a clearing agentand then administration of a “ligand” (e.g. avidin) which is conjugatedto a cytotoxic agent (e.g. a radionuclide).

(ix) Immunoliposomes

The anti-ErbB3 antibodies disclosed herein may also be formulated asimmunoliposomes. Liposomes containing the antibody are prepared bymethods known in the art, such as described in Epstein et al., Proc.Natl. Aced. Sci. USA, 82:3688 (1985); Hwang et al., Proc. Natl. Aced.Sci. USA, 77:4030 (1980); and U.S. Pat. Nos. 4,485,045 and 4,544,545.Liposomes with enhanced circulation time are disclosed in U.S. Pat. No.5,013,556.

Particularly useful liposomes can be generated by the reverse phaseevaporation method with a lipid composition comprisingphosphatidylcholine, cholesterol and PEG-derivatizedphosphatidylethanolamine (PEG-PE). Liposomes are extruded throughfilters of defined pore size to yield liposomes with the desireddiameter. Fab′ fragments of the antibody of the present invention can beconjugated to the liposomes as described in Martin et al. J. Biol. Chem.257: 286-288 (1982) via a disulfide interchange reaction. Achemotherapeutic agent (such as Doxorubicin) is optionally containedwithin the liposome. See Gabizon et al. J. National CancerInst.81(19)1484 (1989)

(x) Antibody Dependent Enzyme Mediated Prodrug Therapy (ADEPT)

The antibody of the present invention may also be used in ADEPT byconjugating the antibody to a prodrug-activating enzyme which converts aprodrug (e.g. a peptidyl chemotherapeutic agent, see WO81/01145) to anactive anti-cancer drug. See, for example, WO 88/07378 and U.S. Pat. No.4,975,278.

The enzyme component of the immunoconjugate useful for ADEPT includesany enzyme capable of acting on a prodrug in such a way so as to covertit into its more active, cytotoxic form.

Enzymes that are useful in the method of this invention include, but arenot limited to, alkaline phosphatase useful for convertingphosphate-containing prodrugs into free drugs; arylsulfatase useful forconverting sulfate-containing prodrugs into free drugs; cytosinedeaminase useful for converting non-toxic 5-fluorocytosine into theanti-cancer drug, 5-fluorouracil; proteases, such as serratia protease,thermolysin, subtilisin, carboxypeptidases and cathepsins (such ascathepsins B and L), that are useful for converting peptide-containingprodrugs into free drugs, D-alanylcarboxypeptidases, useful forconverting prodrugs that contain D-amino acid substituents;carbohydrate-cleaving enzymes such as β-galactosidase and neuraminidaseuseful for converting glycosylated prodrugs into free drugs; β-lactamaseuseful for converting drugs derivatized with β-lactams into free drugs;and penicillin amidases, such as penicillin V amidase or penicillin Gamidase, useful for converting drugs derivatized at their aminenitrogens with phenoxyacetyl or phenylacetyl groups, respectively, intofree drugs. Alternatively, antibodies with enzymatic activity, alsoknown in the art as “abzymes”, can be used to convert the prodrugs ofthe invention into free active drugs (see, e.g., Massey, Nature 328:457-458 (1987)). Antibody-abzyme conjugates can be prepared as describedherein for delivery of the abzyme to a tumor cell population.

The enzymes of this invention can be covalently bound to the anti-ErbB3antibodies by techniques well known in the art such as the use of theheterobifunctional crosslinking reagents discussed above. Alternatively,fusion proteins comprising at least the antigen binding region of anantibody of the invention linked to at least a functionally activeportion of an enzyme of the invention can be constructed usingrecombinant DNA techniques well known in the art (see, e.g., Neubergeret al., Nature, 312: 604-608 (1984)).

(xi) Antibody-Salvage Receptor Binding Epitope Fusions.

In certain embodiments of the invention, it may be desirable to use anantibody fragment, rather than an intact antibody, to increase tumorpenetration, for example. In this case, it may be desirable to modifythe antibody fragment in order to increase its serum half life. This maybe achieved, for example, by incorporation of a salvage receptor bindingepitope into the antibody fragment (e.g. by mutation of the appropriateregion in the antibody fragment or by incorporating the epitope into apeptide tag that is then fused to the antibody fragment at either end orin the middle, e.g., by DNA or peptide synthesis).

A systematic method for preparing such an antibody variant having anincreased in vivo half-life comprises several steps. The first involvesidentifying the sequence and conformation of a salvage receptor bindingepitope of an Fc region of an IgG molecule. Once this epitope isidentified, the sequence of the antibody of interest is modified toinclude the sequence and conformation of the identified binding epitope.After the sequence is mutated, the antibody variant is tested to see ifit has a longer in vivo half-life than that of the original antibody. Ifthe antibody variant does not have a longer in vivo half-life upontesting, its sequence is further altered to include the sequence andconformation of the identified binding epitope. The altered antibody istested for longer in vivo half-life, and this process is continued untila molecule is obtained that exhibits a longer in vivo half-life.

The salvage receptor binding epitope being thus incorporated into theantibody of interest is any suitable such epitope as defined above, andits nature will depend, e.g., on the type of antibody being modified.The transfer is made such that the antibody of interest still possessesthe biological activities described herein.

The epitope generally constitutes a region wherein any one or more aminoacid residues from one or two loops of a Fc domain are transferred to ananalogous position of the antibody fragment. Even more preferably, threeor more residues from one or two loops of the Fc domain are transferred,Still, more preferred, the epitope is taken from the CH2 domain of theFc region (e.g., of an IgG) and transferred to the CH1, CH3, or V_(H)region, or more than one such region, of the antibody. Alternatively,the epitope is taken from the CH2 domain of the Fc region andtransferred to the CL region or V_(L) region, or both, of the antibodyfragment.

In one most preferred embodiment, the salvage receptor binding epitopecomprises the sequence (5′ to 3′): PKNSSMISNTP (SEQ ID NO: 1), andoptionally further comprises a sequence selected from the groupconsisting of HQSLGTQ (SEQ ID NO: 2), HQNLSDGK (SEQ ID NO: 3), HQNISDGK(SEQ ID NO: 4), or VISSHLGQ (SEQ ID NO: 5), particularly where theantibody fragment is a Fab or F(ab′)₂. In another most preferredembodiment, the salvage receptor binding epitope is a polypeptidecontaining the sequence(s)(5′ to 3′): HQNLSDGK (SEQ ID NO: 3), HQNISDGK(SEQ ID NO: 4), or VISSHLGQ (SEQ ID NO: 5) and the sequence: PKNSSMISNTP(SEQ ID NO: 1).

B. Vectors, Host Cells and Recombinant Methods

The invention also provides isolated nucleic acid encoding an antibodyas disclosed herein, vectors and host cells comprising the nucleic acid,and recombinant techniques for the production of the antibody.

For recombinant production of the antibody, the nucleic acid encoding itis isolated and inserted into a replicable vector for further cloning(amplification of the DNA) or for expression. DNA encoding themonoclonal antibody is readily isolated and sequenced using conventionalprocedures (e.g., by using oligonucleotide probes that are capable ofbinding specifically to genes encoding the heavy and light chains of theantibody). Many vectors are available. The vector components generallyinclude, but are not limited to, one or more of the following: a signalsequence, an origin of replication, one or more marker genes, anenhancer element, a promoter, and a transcription termination sequence.

(I) Signal Sequence Component

The anti-ErbB3 antibody of this invention may be produced recombinantlynot only directly, but also as a fusion polypeptide with a heterologouspolypeptide, which is preferably a signal sequence or other polypeptidehaving a specific cleavage site at the N-terminus of the mature proteinor polypeptide. The heterologous signal sequence selected preferably isone that is recognized and processed (i.e., cleaved by a signalpeptidase) by the host cell. For prokaryotic host cells that do notrecognize and process the native anti-ErbB3 antibody signal sequence,the signal sequence is substituted by a prokaryotic signal sequenceselected, for example, from the group of the alkaline phosphatase,penicillinase, Ipp, or heat-stable enterotoxin II leaders. For yeastsecretion the native signal sequence may be substituted by, e.g., theyeast invertase leader, a factor leader (including Saccharomyces andKluyveromyces α-factor leaders), or acid phosphatase leader, the C.albicons glucoamylase leader, or the signal described in WO 90/13646. Inmammalian cell expression, mammalian signal sequences as well as viralsecretory leaders, for example, the herpes simplex gD signal, areavailable.

The DNA for such precursor region is ligated in reading frame to DNAencoding the anti-ErbB3 antibody.

(ii) Origin of Replication Component

Both expression and cloning vectors contain a nucleic acid sequence thatenables the vector to replicate in one or more selected host cells.Generally, in cloning vectors this sequence is one that enables thevector to replicate independently of the host chromosomal DNA, andincludes origins of replication or autonomously replicating sequences.Such sequences are well known for a variety of bacteria, yeast, andviruses. The origin of replication from the plasmid pBR322 is suitablefor most Gram-negative bacteria, the 2μ plasmid origin is suitable foryeast, and various viral origins (SV40, polyoma, adenovirus, VSV or BPV)are useful for cloning vectors in mammalian cells. Generally, the originof replication component is not needed for mammalian expression vectors(the SV40 origin may typically be used only because it contains theearly promoter).

(iii) Selection Gene Component

Expression and cloning vectors may contain a selection gene, also termeda selectable marker. Typical selection genes encode proteins that (a)confer resistance to antibiotics or other toxins, e.g., ampicillin,neomycin, methotrexate, or tetracycline, (b) complement auxotrophicdeficiencies, or (c) supply critical nutrients not available fromcomplex media, e.g., the gene encoding D-alanine racemase for Bacilli.

One example of a selection scheme utilizes a drug to arrest growth of ahost cell. Those cells that are successfully transformed with aheterologous gene produce a protein conferring drug resistance and thussurvive the selection regimen. Examples of such dominant selection usethe drugs neomycin, mycophenolic acid and hygromycin.

Another example of suitable selectable markers for mammalian cells arethose that enable the identification of cells competent to take up theanti-ErbB3 antibody nucleic acid, such as DHFR, thymidine kinase,metallothionein-I and -II, preferably primate metallothionein genes,adenosine deaminase, ornithine decarboxylase, etc.

For example, cells transformed with the DHFR selection gene are firstidentified by culturing all of the transformants in a culture mediumthat contains methotrexate (Mtx), a competitive antagonist of DHFR. Anappropriate host cell when wild-type DHFR is employed is the Chinesehamster ovary (CHO) cell line deficient in DHFR activity.

Alternatively, host cells (particularly wild-type hosts that containendogenous DHFR) transformed or co-transformed with DNA sequencesencoding anti-ErbB3 antibody, wild-type DHFR protein, and anotherselectable marker such as aminoglycoside 3′-phosphotransferase (APH) canbe selected by cell growth in medium containing a selection agent forthe selectable marker such as an aminoglycosidic antibiotic, e.g.,kanamycin, neomycin, or G418. See U.S. Pat. No. 4,965,199.

A suitable selection gene for use in yeast is the trp1 gene present inthe yeast plasmid YRp7 (Stinchcomb et al., Nature, 282:39 (1979)). Thetrp1 gene provides a selection marker for a mutant strain of yeastlacking the ability to grow in tryptophan, for example, ATCC No. 44076or PEP4-1. Jones, Genetics, 85:12 (1977). The presence of the trp1lesion in the yeast host cell genome then provides an effectiveenvironment for detecting transformation by growth in the absence oftryptophan. Similarly, Leu2-deficient yeast strains (ATCC 20,622 or38,626) are complemented by known plasmids bearing the Leu2 gene.

In addition, vectors derived from the 1.6 μm circular plasmid pKD1 canbe used for transformation of Kluyveromyces yeasts, Alternatively, anexpression system for large-scale production of recombinant calfchymosin was reported for K. lactis. Van den Berg, Bio/Technology, 8:135(1990). Stable multi-copy expression vectors for secretion of maturerecombinant human serum albumin by industrial strains of Kluyveromyceshave also been disclosed. Fleer et al., Bio/Technology, 9:968-975(1991).

(iv) Promoter Component

Expression and cloning vectors usually contain a promoter that isrecognized by the host organism and is operably linked to the anti-ErbB3antibody nucleic acid. Promoters suitable for use with prokaryotic hostsinclude the phoA promoter, β-lactamase and lactose promoter systems,alkaline phosphatase, a tryptophan (trp) promoter system, and hybridpromoters such as the tac promoter. However, other known bacterialpromoters are suitable. Promoters for use in bacterial systems also willcontain a Shine-Dalgarno (S.D.) sequence operably linked to the DNAencoding the anti-ErbB3 antibody.

Promoter sequences are known for eukaryotes. Virtually all eukaryoticgenes have an AT-rich region located approximately 25 to 30 basesupstream from the site where transcription is initiated. Anothersequence found 70 to 80 bases upstream from the start of transcriptionof many genes is a CNCAAT region where N may be any nucleotide. At the3′ end of most eukaryotic genes is an AATAAA sequence that may be thesignal for addition of the poly A tail to the 3′ end of the codingsequence. All of these sequences are suitably inserted into eukaryoticexpression vectors.

Examples of suitable promoting sequences for use with yeast hostsinclude the promoters for 3-phosphoglycerate kinase or other glycolyticenzymes, such as enolase, glyceraldehyde-3-phosphate dehydrogenase,hexokinase, pyruvate decarboxylase, phosphofructokinase,glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvatekinase, triosephosphate isomerase, phosphoglucose isomerase, andglucokinase.

Other yeast promoters, which are inducible promoters having theadditional advantage of transcription controlled by growth conditions,are the promoter regions for alcohol dehydrogenase 2, isocytochrome C,acid phosphatase, degradative enzymes associated with nitrogenmetabolism, metallothionein, glyceraldehyde-3-phosphate dehydrogenase,and enzymes responsible for maltose and galactose utilization. Suitablevectors and promoters for use in yeast expression are further describedin EP 73,657. Yeast enhancers also are advantageously used with yeastpromoters.

Anti-ErbB3 antibody transcription from vectors in mammalian host cellsis controlled, for example, by promoters obtained from the genomes ofviruses such as polyoma virus, fowlpox virus, adenovirus (such asAdenovirus 2), bovine papilloma virus, avian sarcoma virus,cytomegalovirus, a retrovirus, hepatitis-B virus and most preferablySimian Virus 40 (SV40), from heterologous mammalian promoters, e.g., theactin promoter or an immunoglobulin promoter, from heat-shock promoters,provided such promoters are compatible with the host cell systems.

The early and late promoters of the SV40 virus are conveniently obtainedas an SV40 restriction fragment that also contains the SV40 viral originof replication. The immediate early promoter of the humancytomegalovirus is conveniently obtained as a HindIII E restrictionfragment. A system for expressing DNA in mammalian hosts using thebovine papilloma virus as a vector is disclosed in U.S. Pat. No.4,419,446. A modification of this system is described in U.S. Pat. No.4,601,978. See also Reyes et al., Nature, 297:598-601 (1982) onexpression of human β-interferon cDNA in mouse cells under the controlof a thymidine kinase promoter from herpes simplex virus. Alternatively,the rous sarcoma virus long terminal repeat can be used as the promoter.

(v) Enhancer Element Component

Transcription of a DNA encoding the anti-ErbB3 antibody of thisinvention by higher eukaryotes is often increased by inserting anenhancer sequence into the vector. Many enhancer sequences are now knownfrom mammalian genes (globin, elastase, albumin, α-fetoprotein, andinsulin). Typically, however, one will use an enhancer from a eukaryoticcell virus. Examples include the SV40 enhancer on the late side of thereplication origin (bp 100-270), the cytomegalovirus early promoterenhancer, the polyoma enhancer on the late side of the replicationorigin, and adenovirus enhancers. See also Yaniv, Nature, 297:17-18(1982) on enhancing elements for activation of eukaryotic promoters. Theenhancer may be spliced into the vector at a position 5′ or 3′ to theanti-ErbB3 antibody-encoding sequence, but is preferably located at asite 5′ from the promoter.

(vi) Transcription Termination Component

Expression vectors used in eukaryotic host cells (yeast, fungi, insect,plant, animal, human, or nucleated cells from other multicellularorganisms) will also contain sequences necessary for the termination oftranscription and for stabilizing the mRNA, Such sequences are commonlyavailable from the 5′ and, occasionally 3′, untranslated regions ofeukaryotic or viral DNAs or cDNAs. These regions contain nucleotidesegments transcribed as polyadenylated fragments in the untranslatedportion of the mRNA encoding anti-ErbB3 antibody. One usefultranscription termination component is the bovine growth hormonepolyadenylation region. See WO94/11026 and the expression vectordisclosed therein. (vii) Selection and transformation of host cells

Suitable host cells for cloning or expressing the DNA in the vectorsherein are the prokaryote, yeast, or higher eukaryote cells describedabove. Suitable prokaryotes for this purpose include eubacteria, such asGram-negative or Gram-positive organisms, for example,Enterobacteriaceae such as Escherichia, e.g., E. coli, Enterobacter,Erwinia, Klebsiella, Proteus, Salmonella, e.g., Salmonella typhimurium,Serratia, e.g., Serratia marcescans, and Shigella, as well as Bacillisuch as B. subtilis and B. licheniformis (e.g., B. licheniformis 41 Pdisclosed in DD 266,710 published 12 Apr. 1989), Pseudomonas such as P.aeruginosa, and Streptomyces. One preferred E. coli cloning host is E.coli 294 (ATCC 31,446), although other strains such as E. coli B, E.coli X1776 (ATCC 31,537), and E. coli W3110 (ATCC 27,325) are suitable.These examples are illustrative rather than limiting.

In addition to prokaryotes, eukaryotic microbes such as filamentousfungi or yeast are suitable cloning or expression hosts for anti-ErbB3antibody-encoding vectors. Saccharomyces cerevisiae, or common baker'syeast, is the most commonly used among lower eukaryotic hostmicroorganisms. However, a number of other genera, species, and strainsare commonly available and useful herein, such as Schizosaccharomycespombe; Kluyveromyces hosts such as, e.g., K lactis, K. fragilis (ATCC12,424), K. bulgaricus (ATCC 16,045), K. wickeramii (ATCC 24,178), K.waltii (ATCC 56,500), K. drosophilarum (ATCC 36,906), K. thermotolerans,and K. marxianus, yarrowia (EP 402,226); Pichia pastoris (EP 183,070),Candida; Trichoderma reesia (EP 244,234); Neurospora crossa,Schwanniomyces such as Schwanniomyces occidentalis, and filamentousfungi such as, e.g., Neurospora, Penicillium, Tolypocladium, andAspergillus hosts such as A. nidulans and A. niger.

Suitable host cells for the expression of glycosylated anti-ErbB3antibody are derived from multicellular organisms. Examples ofinvertebrate cells include plant and insect cells. Numerous baculoviralstrains and variants and corresponding permissive insect host cells fromhosts such as Spodoptera frugiperda (caterpillar), Aedes aegypti(mosquito), Aedes albopictus (mosquito), Drosophila melanogaster(fruitfly), and Bombyx mori have been identified. A variety of viralstrains for transfection are publicly available, e.g., the L-1 variantof Autographa californica NPV and the Bm-5 strain of Bombyx mori NPV,and such viruses may be used as the virus herein according to thepresent invention, particularly for transfection of Spodopterafrugiperda cells.

Plant cell cultures of cotton, corn, potato, soybean, petunia, tomato,and tobacco can also be utilized as hosts.

However, interest has been greatest in vertebrate cells, and propagationof vertebrate cells in culture (tissue culture) has become a routineprocedure. Examples of useful mammalian host cell lines are monkeykidney CV1 line transformed by SV40 (COS-7, ATCC CRL 1651); humanembryonic kidney line (293 or 293 cells subcloned for growth insuspension culture, Graham et al., J. Gen Virol., 36:59 (1977)); babyhamster kidney cells (BHK, ATCC CCL 10); Chinese hamster ovarycells/-DHFR(CHO, Urlaub et al., Proc. Natl. Acad. Sci. USA, 77:4216(1980)); mouse sertoli cells (TM4, Mather, Biol. Reprod., 23:243-251(1980)); monkey kidney cells (CV1 ATCC CCL 70); African green monkeykidney cells (VERO-76, ATCC CRL-1587); human cervical carcinoma cells(HELA, ATCC CCL 2); canine kidney cells (MDCK, ATCC CCL 34); buffalo ratliver cells (BRL 3A, ATCC CRL 1442); human lung cells (WI 38, ATCC CCL75); human liver cells (Hep G2, HB 8065); mouse mammary tumor (MMT060562, ATCC CCL51); TRI cells (Mather et al., Annals N.Y. Acad. Sci.,383:44-68 (1982)); MRC 5 cells; FS4 cells; and a human hepatoma line(Hep G2).

Host cells are transformed with the above-described expression orcloning vectors for anti-ErbB3 antibody production and cultured inconventional nutrient media modified as appropriate for inducingpromoters, selecting transformants, or amplifying the genes encoding thedesired sequences.

(viii) Culturing the Host Cells

The host cells used to produce the anti-ErbB3 antibody of this inventionmay be cultured in a variety of media. Commercially available media suchas Ham's F10 (Sigma), Minimal Essential Medium ((MEM), (Sigma),RPMI-1640 (Sigma), and Dulbecco's Modified Eagle's Medium ((DMEM),Sigma) are suitable for culturing the host cells. In addition, any ofthe media described in Ham et al. Meth. Enz., 58:44 (1979), Barnes etal., Anal. Biochem., 102:255 (1980), U.S. Pat. Nos. 4,767,704;4,657,866; 4,927,762; 4,560,655; or 5,122,469; WO 90/03430; WO 87/00195;or U.S. Pat. Re. 30,985 may be used as culture media for the host cells,Any of these media may be supplemented as necessary with hormones and/orother growth factors (such as insulin, transferring or epidermal growthfactor), salts (such as sodium chloride, calcium, magnesium, andphosphate), buffers (such as HEPES), nucleotides (such as adenosine andthymidine), antibiotics (such as GENTAMYCIN™ drug), trace elements(defined as inorganic compounds usually present at final concentrationsin the micromolar range), and glucose or an equivalent energy source.Any other necessary supplements may also be included at appropriateconcentrations that would be known to those skilled in the art. Theculture conditions, such as temperature, pH, and the like, are thosepreviously used with the host cell selected for expression, and will beapparent to the ordinarily skilled artisan,

(ix) Purification of Anti-ErbB3 Antibody

When using recombinant techniques, the antibody can be producedintracellularly, in the periplasmic space, or directly secreted into themedium. If the antibody is produced intracellularly, as a first step,the particulate debris, either host cells or lysed fragments, isremoved, for example, by centrifugation or ultrafiltration. Carter etal., Bio/Technology 10:163-167 (1992) describe a procedure for isolatingantibodies which are secreted to the periplasmic space of E. coliBriefly, cell paste is thawed in the presence of sodium acetate (pH3.5), EDTA, and phenylmethylsulfonylfluoride (PMSF) over about 30 min.Cell debris can be removed by centrifugation. Where the antibody issecreted into the medium, supernatants from such expression systems aregenerally first concentrated using a commercially available proteinconcentration filter, for example, an Amicon or Millipore Pelliconultrafiltration unit. A protease inhibitor such as PMSF may be includedin any of the foregoing steps to inhibit proteolysis and antibiotics maybe included to prevent the growth of adventitious contaminants.

The antibody composition prepared from the cells can be purified using,for example, hydroxylapatite chromatography, gel electrophoresis,dialysis, and affinity chromatography, with affinity chromatographybeing the preferred purification technique. The suitability of protein Aas an affinity ligand depends on the species and isotype of anyimmunoglobulin Fc domain that is present in the antibody. Protein A canbe used to purify antibodies that are based on human y1, y2, or y4 heavychains (Lindmark et al., J. Immunol. Meth. 62:1-13 (1983)). Protein G isrecommended for all mouse isotypes and for human y3 (Guss et al., EMBOJ. 5:15671575 (1986)). The matrix to which the affinity ligand isattached is most often agarose, but other matrices are available,Mechanically stable matrices such as controlled pore glass orpoly(styrenedivinyl)benzene allow for faster flow rates and shorterprocessing times than can be achieved with agarose. Where the antibodycomprises a C_(H)3 domain, the Bakerbond ABX™ resin (J. T. Baker,Phillipsburg, N.J.) is useful for purification. Other techniques forprotein purification such as fractionation on an ion-exchange column,ethanol precipitation, Reverse Phase HPLC, chromatography on silica,chromatography on heparin Sepharose™ chromatography on an anion orcation exchange resin (such as a polyaspartic acid column),chromatofocusing, SDS-PAGE, and ammonium sulfate precipitation are alsoavailable depending on the antibody to be recovered.

Following any preliminary purification step(s), the mixture comprisingthe antibody of interest and contaminants may be subjected to low pHhydrophobic interaction chromatography using an elution buffer at a pHbetween about 2.5-4.5, preferably performed at low salt concentrations(e.g. from about 0-0.25M salt).

C. Pharmaceutical Formulations

Therapeutic formulations of the antibody are prepared for storage bymixing the antibody having the desired degree of purity with optionalphysiologically acceptable carriers, excipients or stabilizers(Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980)),in the form of lyophilized formulations or aqueous solutions. Acceptablecarriers, excipients, or stabilizers are nontoxic to recipients at thedosages and concentrations employed, and include buffers such asphosphate, citrate, and other organic acids; antioxidants includingascorbic acid and methionine; preservatives (such asoctadecyldimethylbenzyl ammonium chloride; hexamethonium chloride;benzalkonium chloride, benzethonium chloride; phenol, butyl or benzylalcohol; alkyl parabens such as methyl or propyl paraben; catechol;resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecularweight (less than about 10 residues) polypeptides; proteins, such asserum albumin, gelatin, or immunoglobulins; hydrophilic polymers such aspolyvinylpyrrolidone; amino acids such as glycine, glutamine,asparagine, histidine, arginine, or lysine; monosaccharides,disaccharides, and other carbohydrates including glucose, mannose, ordextrins; chelating agents such as EDTA; sugars such as sucrose,mannitol, trehalose or sorbitol; salt-forming counter-ions such assodium; metal complexes (e.g. Zn-protein complexes); and/or non-ionicsurfactants such as Tween™, Pluronics™ or polyethylene glycol (PEG).

The formulation herein may also contain more than one active compound asnecessary for the particular indication being treated, preferably thosewith complementary activities that do not adversely affect each other.For example, it may be desirable to further provide antibodies whichbind to EGFR, ErbB2, ErbB4, or vascular endothelial factor (VEGF) in theone formulation. Alternatively, or in addition, the composition maycomprise a chemotherapeutic agent or a cytokine. Such molecules aresuitably present in combination in amounts that are effective for thepurpose intended.

The active ingredients may also be entrapped in microcapsules prepared,for example, by coacervation techniques or by interfacialpolymerization, for example, hydroxymethylcellulose orgelatin-microcapsules and poly-(methylmethacylate) microcapsules,respectively, in colloidal drug delivery systems (for example,liposomes, albumin microspheres, microemulsions, nano-particles andnanocapsules) or in macroemulsions. Such techniques are disclosed inRemington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980).

The formulations to be used for in vivo administration must be sterile.This is readily accomplished by filtration through sterile filtrationmembranes.

Sustained-release preparations may be prepared. Suitable examples ofsustained-release preparations include semipermeable matrices of solidhydrophobic polymers containing the antibody, which matrices are in theform of shaped articles, e.g. films, or microcapsules. Examples ofsustained-release matrices include polyesters, hydrogels (for example,poly(2-hydroxyethyl-methacrylate), or poly(vinylalcohol)), polylactides(U.S. Pat. No. 3,773,919), copolymers of L-glutamic acid and yethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradablelactic acid-glycolic acid copolymers such as the Lupron Depot™(injectable microspheres composed of lactic acid-glycolic acid copolymerand leuprolide acetate), and poly-D-(−)-3-hydroxybutyric acid. Whilepolymers such as ethylene-vinyl acetate and lactic acid-glycolic acidenable release of molecules for over 100 days, certain hydrogels releaseproteins for shorter time periods. When encapsulated antibodies remainin the body for a long time, they may denature or aggregate as a resultof exposure to moisture at 37° C., resulting in a loss of biologicalactivity and possible changes in immunogenicity. Rational strategies canbe devised for stabilization depending on the mechanism involved. Forexample, if the aggregation mechanism is discovered to be intermolecularS—S bond formation through thio-disulfide interchange, stabilization maybe achieved by modifying sulfhydryl residues, lyophilizing from acidicsolutions, controlling moisture content, using appropriate additives,and developing specific polymer matrix compositions.

D. Non-Therapeutic Uses for the Antibody

The antibodies of the invention may be used as affinity purificationagents. In this process, the antibodies are immobilized on a solid phasesuch a Sephadex resin or filter paper, using methods well known in theart. The immobilized antibody is contacted with a sample containing theErbB3 protein (or fragment thereof) to be purified, and thereafter thesupport is washed with a suitable solvent that will remove substantiallyall the material in the sample except the ErbB3 protein, which is boundto the immobilized antibody. Finally, the support is washed with anothersuitable solvent, such as glycine buffer, pH 5.0, that will release theErbB3 protein from the antibody.

Anti-ErbB3 antibodies may also be useful in diagnostic assays for ErbB3protein, e.g., detecting its expression in specific cells, tissues, orserum. Thus, the antibodies may be used in the diagnosis of humanmalignancies (see, for example, U.S. Pat. No. 5,183,884).

For diagnostic applications, the antibody typically will be labeled witha detectable moiety. Numerous labels are available which can begenerally grouped into the following categories:

(a) Radioisotopes, such as ³⁵S, ¹⁴C, ¹²⁵I, ³H, and ¹³¹I The antibody canbe labeled with the radioisotope using the techniques described inCurrent Protocols in Immunology, Volumes 1 and 2, Coligen et al., Ed.,Wiley-Interscience, New York, N.Y., Pubs., (1991) for example andradioactivity can be measured using scintillation counting.

(b) Fluorescent labels such as rare earth chelates (europium chelates)or fluorescein and its derivatives, rhodamine and its derivatives,dansyl, Lissamine, phycoerythrin and Texas Red are available, Thefluorescent labels can be conjugated to the antibody using thetechniques disclosed in Current Protocols in Immunology, supra, forexample. Fluorescence can be quantified using a fluorimeter,

(c) Various enzyme-substrate labels are available and U.S. Pat. No.4,275,149 provides a review of some of these. The enzyme generallycatalyses a chemical alteration of the chromogenic substrate which canbe measured using various techniques. For example, the enzyme maycatalyze a color change in a substrate, which can be measuredspectrophotometrically. Alternatively, the enzyme may alter thefluorescence or chemiluminescence of the substrate. Techniques forquantifying a change in fluorescence are described above. Thechemiluminescent substrate becomes electronically excited by a chemicalreaction and may then emit light which can be measured (using achemiluminometer, for example) or donates energy to a fluorescentacceptor. Examples of enzymatic labels include luciferases (e.g.,firefly luciferase and bacterial luciferase; U.S. Pat. No. 4,737,456),luciferin, 2,3-dihydrophthalazinediones, malate dehydrogenase, urease,peroxidase such as horseradish peroxidase (HRPO), alkaline phosphatase,β-galactosidase, glucoamylase, lysozyme, saccharide oxidases (e.g.,glucose oxidase, galactose oxidase, and glucose-6-phosphatedehydrogenase), heterocyclic oxidases (such as uricase and xanthineoxidase), lactoperoxidase, microperoxidase, and the like. Techniques forconjugating enzymes to antibodies are described in O'Sullivan et al.,Methods for the Preparation of Enzyme-Antibody Conjugates for use inEnzyme Immunoassay, in Methods in Enzym. (ed J. Langone & H. VanVunakis), Academic press, New York, 73: 147-166 (1981).

Examples of enzyme-substrate combinations include, for example:

(i) Horseradish peroxidase (HRPO) with hydrogen peroxidase as asubstrate, wherein the hydrogen peroxidase oxidizes a dye precursor(e.g. orthophenylene diamine (OPD) or 3,3′,5,5′-tetramethyl benzidinehydrochloride (TMB));

(ii) alkaline phosphatase (AP) with para-Nitrophenyl phosphate aschromogenic substrate; and

(iii) β-D-galactosidase (β-D-Gal) with a chromogenic substrate (e.g.p-nitrophenyl-β-D-galactosidase) or fluorogenic substrate4-methylumbelliferyl-β-D-galactosidase.

Numerous other enzyme-substrate combinations are available to thoseskilled in the art. For a general review of these, see U.S. Pat. Nos.4,275,149 and 4,318,980.

Sometimes, the label is indirectly conjugated with the antibody. Theskilled artisan will be aware of various techniques for achieving this.For example, the antibody can be conjugated with biotin and any of thethree broad categories of labels mentioned above can be conjugated withavidin, or vice versa. Biotin binds selectively to avidin and thus, thelabel can be conjugated with the antibody in this indirect manner.Alternatively, to achieve indirect conjugation of the label with theantibody, the antibody is conjugated with a small hapten (e.g. digoxin)and one of the different types of labels mentioned above is conjugatedwith an anti-hapten antibody (e.g. anti-digoxin antibody). Thus,indirect conjugation of the label with the antibody can be achieved.

In another embodiment of the invention, the anti-ErbB3 antibody need notbe labeled, and the presence thereof can be detected using a labeledantibody which binds to the ErbB3 antibody.

The antibodies of the present invention may be employed in any knownassay method, such as competitive binding assays, direct and indirectsandwich assays, and immunoprecipitation assays. Zola, MonoclonalAntibodies: A Manual of Techniques, pp. 147-158 (CRC Press, Inc., 1987).

Competitive binding assays rely on the ability of a labeled standard tocompete with the test sample analyte for binding with a limited amountof antibody. The amount of ErbB3 protein in the test sample is inverselyproportional to the amount of standard that becomes bound to theantibodies. To facilitate determining the amount of standard thatbecomes bound, the antibodies generally are insolubilized before orafter the competition, so that the standard and analyte that are boundto the antibodies may conveniently be separated from the standard andanalyte which remain unbound.

Sandwich assays involve the use of two antibodies, each capable ofbinding to a different immunogenic portion, or epitope, of the proteinto be detected. In a sandwich assay, the test sample analyte is bound bya first antibody which is immobilized on a solid support, and thereaftera second antibody binds to the analyte, thus forming an insolublethree-part complex. See, e.g., U.S. Pat. No. 4,376,110. The secondantibody may itself be labeled with a detectable moiety (direct sandwichassays) or may be measured using an anti-immunoglobulin antibody that islabeled with a detectable moiety (indirect sandwich assay). For example,one type of sandwich assay is an ELISA assay, in which case thedetectable moiety is an enzyme.

For immunohistochemistry, the tumor sample may be fresh or frozen or maybe embedded in paraffin and fixed with a preservative such as formalin,for example.

The antibodies may also be used for in vivo diagnostic assays.Generally, the antibody is labelled with a radionuclide (such as ¹¹¹In,⁹⁹Tc, ¹⁴C, ¹³¹I, ¹²⁵I, ³H, ³²P or ³⁵S) so that the tumor can belocalized using immunoscintiography.

E. Diagnostic Kits

As a matter of convenience, the antibody of the present invention can beprovided in a kit, i.e., a packaged combination of reagents inpredetermined amounts with instructions for performing the diagnosticassay. Where the antibody is labelled with an enzyme, the kit willinclude substrates and cofactors required by the enzyme (e.g. asubstrate precursor which provides the detectable chromophore orfluorophore). In addition, other additives may be included such asstabilizers, buffers (e.g. a block buffer or lysis buffer) and the like.The relative amounts of the various reagents may be varied widely toprovide for concentrations in solution of the reagents whichsubstantially optimize the sensitivity of the assay. Particularly, thereagents may be provided as dry powders, usually lyophilized, includingexcipients which on dissolution will provide a reagent solution havingthe appropriate concentration.

F. Therapeutic Uses for the Antibody

It is contemplated that the anti-ErbB3 antibody of the present inventionmay be used to treat conditions in which excessive activation of theErbB2-ErbB3 complex is occurring, particularly where such activation ismediated by a heregulin polypeptide. Exemplary conditions or disordersto be treated with the ErbB3 antibody include benign or malignant tumors(e.g. renal, liver, kidney, bladder, breast, gastric, ovarian,colorectal, prostate, pancreatic, ling, vulval, thyroid, hepaticcarcinomas; sarcomas; glioblastomas; and various head and neck tumors);leukemias and lymphoid malignancies; other disorders such as neuronal,glial, astrocytal, hypothalamic and other glandular, macrophagal,epithelial, stromal and blastocoelic disorders; and inflammatory,angiogenic and immunologic disorders.

The antibodies of the invention are administered to a mammal, preferablya human, in accord with known methods, such as intravenousadministration as a bolus or by continuous infusion over a period oftime, by intramuscular, intraperitoneal, intracerobrospinal,subcutaneous, intra-articular, intrasynovial, intrathecal, oral,topical, or inhalation routes. Intravenous administration of theantibody is preferred.

Other therapeutic regimens may be combined with the administration ofthe anti-ErbB3 antibodies of the instant invention. For example, thepatient to be treated with the antibodies disclosed herein may alsoreceive radiation therapy. Alternatively, or in addition, achemotherapeutic agent may be administered to the patient. Preparationand dosing schedules for such chemotherapeutic agents may be usedaccording to manufacturers' instructions or as determined empirically bythe skilled practitioner. Preparation and dosing schedules for suchchemotherapy are also described in Chemotherapy Service Ed., M.C. Perry,Williams & Wilkins, Baltimore, Md. (1992). The chemotherapeutic agentmay precede, or follow administration of the antibody or may be givensimultaneously therewith.

It may be desirable to also administer antibodies against other tumorassociated antigens, such as antibodies which bind to the EGFR, ErbB2,ErbB4, or vascular endothelial factor (VEGF). Two or more anti-ErbB3antibodies may be co-administered to the patient. Alternatively, or inaddition one or more cytokines may be administered to the patient.

For the prevention or treatment of disease, the appropriate dosage ofantibody will depend on the type of disease to be treated, as definedabove, the severity and course of the disease, whether the antibody isadministered for preventive or therapeutic purposes, previous therapy,the patient's clinical history and response to the antibody, and thediscretion of the attending physician. The antibody is suitablyadministered to the patient at one time or over a series of treatments.

Depending on the type and severity of the disease, about 1 μg/kg to 15mg/kg (e.g. 0.1-20 mg/kg) of antibody is an initial candidate dosage foradministration to the patient, whether, for example, by one or moreseparate administrations, or by continuous infusion. A typical dailydosage might range from about 1 μg/kg to 100 mg/kg or more, depending onthe factors mentioned above. For repeated administrations over severaldays or longer, depending on the condition, the treatment is sustaineduntil a desired suppression of disease symptoms occurs. However, otherdosage regimens may be useful. The progress of this therapy is easilymonitored by conventional techniques and assays.

G. Articles of Manufacture

In another embodiment of the invention, an article of manufacturecontaining materials useful for the treatment of the disorders describedabove is provided. The article of manufacture comprises a container anda label. Suitable containers include, for example, bottles, vials,syringes, and test tubes. The containers may be formed from a variety ofmaterials such as glass or plastic. The container holds a compositionwhich is effective for treating the condition and may have a sterileaccess port (for example the container may be an intravenous solutionbag or a vial having a stopper pierceable by a hypodermic injectionneedle). The active agent in the composition is the anti-ErbB3 antibody.The label on, or associated with, the container indicates that thecomposition is used for treating the condition of choice. The article ofmanufacture may further comprise a second container comprising apharmaceutically-acceptable buffer, such as phosphate-buffered saline,Ringer's solution and dextrose solution. It may further include othermaterials desirable from a commercial and user standpoint, includingother buffers, diluents, filters, needles, syringes, and package insertswith instructions for use.

H. Deposit of Materials

The following hybridoma cell line has been deposited with the AmericanType Culture Collection, 12301 Parklawn Drive, Rockville, Md., USA(ATCC): Hybridoma/Antibody Designation ATCC No. Deposit Date 8B8 HB12070Mar. 22, 1996

Hybridoma/Antibody Designation ATCC No. Deposit Date

8B8 HB12070 Mar. 22, 1996

This deposit was made under the provisions of the Budapest Treaty on theInternational Recognition of the Deposit of Microorganisms for thePurpose of Patent Procedure and the Regulations thereunder (BudapestTreaty). This assures maintenance of a viable culture for 30 years fromthe date of deposit. The cell line will be made available by ATCC underthe terms of the Budapest Treaty, and subject to an agreement betweenGenentech, Inc. and ATCC, which assures (a) that access to the culturewill be available during pendency of the patent application to onedetermined by the Commissioner to be entitled thereto under 37 CFR §1.14 and 35 USC §122, and (b) that all restrictions on the availabilityto the public of the culture so deposited will be irrevocably removedupon the granting of the patent.

The assignee of the present application has agreed that if the cultureon deposit should die or be lost or destroyed when cultivated undersuitable conditions, it will be promptly replaced on notification with aviable specimen of the same culture. Availability of the deposited cellline is not to be construed as a license to practice the invention incontravention of the rights granted under the authority of anygovernment in accordance with its patent laws.

The foregoing written specification is considered to be sufficient toenable one skilled in the art to practice the invention. The presentinvention is not to be limited in scope by the culture deposited, sincethe deposited embodiment is intended as a single illustration of oneaspect of the invention and any culture that is functionally equivalentis within the scope of this invention. The deposit of material hereindoes not constitute an admission that the written description hereincontained is inadequate to enable the practice of any aspect of theinvention, including the best mode thereof, nor is it to be construed aslimiting the scope of the claims to the specific illustration that itrepresents. Indeed, various modifications of the invention in additionto those shown and described herein will become apparent to thoseskilled in the art from the foregoing description and fall within thescope of the appended claims.

The following examples are offered by way of illustration and not by wayof limitation. The disclosures of all citations in the specification areexpressly incorporated herein by reference.

EXAMPLE Production of Anti-ErbB3 Antibodies

This example describes the production of the anti-ErbB3 antibodieshaving the characteristics described herein.

Materials and Methods

Cell Lines. The human myeloid leukemia cell line K562 (which lacks classI subfamily receptor protein tyrosine kinases as determined by Northernblotting) and human ovarian carcinoma cell line Caov3 were obtained fromthe American Type Culture Collection (Rockville, Md.). Both werecultured in RPMI 1640 medium supplemented with 10% fetal bovine serum, 2mM glutamine, 100 U/mL penicillin, 100 μg/mL streptomycin, and 10 mMHEPES (“growth medium”).

Stable Transfection of K562 Cells. The K562 cell line was transfectedand ErbB3 expressing clones were selected for. Briefly, erbB3 cDNA wassubcloned into the pcDNA-3 mammalian cell expression vector (Invitrogen)and introduced into K562 cells by electroporation (1180 mF, 350 V).Transfected cells were cultured in growth medium containing 0.8 mg/mLG418. Resistant clones were obtained by limiting dilution and tested forErbB3 expression by Western blot and heregulin (HRG) binding assays. TheErbB3 expressing clone 4E9H3 was used in the experiments described inthis report. Phorbol ester stimulation was found to significantlyenhance ErbB3 expression in the K562 transfectants. Therefore, the 4E9H3cells were placed in growth medium containing 10 ng/mLphorbol-12-myristate acetate (PMA) overnight prior to use in the variousassays described below.

Antibodies. Monoclonal antibodies specific for ErbB3 protein weregenerated against a recombinant fragment of the receptor correspondingto the extracellular domain (ECD) thereof fused at its amino terminus tothe herpes simplex virus type I (HSV I) glycoprotein D (gD) epitope forthe monoclonal antibody 5B6. The coding sequence for the signal sequenceof ErbB3 was replaced with a sequence encoding amino acids 1-53 of thegD polypeptide. Amino acids 1-25 encode the signal sequence of gD whileamino acids 26-53 contain an epitope for the monoclonal antibody 5B6.See WO 95/14776. The resulting construct, gD.Erb3.ECD, was purifiedusing an anti-gD antibody affinity column. Immunizations were performedas follows. Female Balb/c mice (Charles River) were initially injectedvia footpad with 5 μg of gD.ErbB3.ECD in 100 μl RIBI'S™ adjuvant (RibiImmunochemResearch, Inc., Hamilton, Mont.). The animals were boosted 2times with 5 μg of gD.ErbB3.ECD in their footpad every two weeksfollowed by a final footpad injection of 5 μg of gD.ErbB3.ECD. Threedays after the last immunization, popliteal lymph nodes were removed anda single cell suspension was prepared for PEG fusion.

Monoclonal antibodies were purified and tested by immobilized andsolution phase ELISA for cross-reactivity with ErbB2 and ErbB4. For theimmobilized ELISA, 1 μg/ml of ErbB2.ECD, gD.ErbB3.ECD or gD.ErbB4.ECDwas used to coat a 96 well microtiter plate overnight. Anti-ErbB3 Mab at1 μg/ml was added and incubated for 1 hour at room temperature (RT),washed and followed by goat anti-mouse (gam) IgG conjugated to HRPO. TheELISA was developed and read at 490 nm. For the solution phase ELISA, 1μg/ml of gam IgG (Fc specific) was used to coat a 96 well microtiterplate overnight. Anti-ErbB3 Mab at 1 μg/ml was added and incubated for 1hour at RT, washed and followed by biotinylated ErbB2.ECD, gD.ErbB3.ECDor gD.ErbB4.ECD. This reaction was incubated for 1 hour at RT, washedand followed by HRPO strepavidin. The ELISA was developed and read at490 nm. In this assay, none of the anti-ErbB3 antibodies cross-reactedwith ErbB2 or ErbB4.

Fab fragments of the 3-8D6 antibody were generated by papain digestion.Undigested IgG and Fc fragments were removed by protein A affinitychromatography followed by gel filtration chromatography. No IgG wasdetectable in the Fab pool by SDS-PAGE and by a Western blot probed withan Fc specific antibody.

HRG Binding Assays. All HRG binding experiments were carried out usingthe EGF-like domain of the β1 isoform, i.e. HRGβ1₁₇₇₋₂₄₄(Sliwkowski etal., J. Biol. Chem. 269: 14661-5 (1994)). The ErbB3 antibody panel wasscreened for an effect on HRG binding by incubating 5.0×10⁴ 4E9H3 cellswith 100 pM ¹²⁵I-HRG overnight at 0° C., in the absence (control) orpresence of 100 nM anti-ErbB3 antibody. Irrelevant IgGs were used asnegative controls. The cells were harvested and rapidly washed with icecold assay buffer (RPMI medium containing 10 mM HEPES, pH=7.2) in a 96well filtration device (Millipore). The filters were then removed andcounted.

For the antibody dose-response experiments, 4E9H3 cells were incubatedwith 100 pM ¹²⁵I-HRGin the presence of increasing concentrations ofantibody. HRG affinity measurements were determined in the absence(control) or presence of either 100 nM antibody or Fab fragment. Theseexperiments were carried out in a competitive inhibition format withincreasing amounts of unlabeled HRG and a fixed concentration (35 pM) of¹²⁵I-HRG. For the control experiment (no antibody) 1×10⁵ 4E9H3 cellswere used for each sample. Due to limitations in the dynamic range ofthe assay, the number of 4E9H3 cells used for binding in the presence ofeither the antibody or the Fab was reduced to 2.5×10⁴ cells per sample.

Antibody reduction of HRG stimulated phosphorylation. Caov3 cells, whichnaturally express ErbB2 and ErbB3, were pre-incubated with 250 nManti-ErbB3 antibody 3-8D6, Fab fragments of this antibody, or buffer(control), for 60 minutes at room temperature. The anti-ErbB2 antibody,2C4 (Fendly et al., Cancer Res., 50:1550-1558 (1990)), which waspreviously shown to block HRG stimulated phosphorylation of ErbB2 wasincluded as a positive control, The cells were then stimulated with HRGat a final concentration of 10 nM for 8 minutes at room temperature, orleft unstimulated. The reaction was stopped by removing the supernatantsand dissolving the cells in SDS sample buffer, The lysates were then runon SDS-PAGE. Western blots of the gels were probed withanti-phosphotyrosine conjugated to horseradish peroxidase (TransductionLabs), and the blots were visualized using a chemiluminescent substrate(Amersham). The blots were scanned with a reflectance scanningdensitometer as described in Holmes et al., Science, 256:1205-1210(1992).

Antibody reduction of ErbB2-ErbB3 protein complex formation. Caov3 cellswere pre-incubated with buffer (control), 250 nM anti-ErbB3 antibody3-8D6, or Fab fragments of this antibody, or the anti-ErbB2 antibody(2C4) for 60 minutes at room temperature, then treated with 10 nM HRG orcontrol buffer for 10 minutes. The cells were lysed in 25 mM Tris,pH=7.5, 150 mM NaCl, 1 mM EDTA, 1.0% Triton X-100™, 1.0% CHAPS, 10% v/vglycerol, containing 0.2 mM PMSF, 50 mTU/mL aprotinin, and 10 mMleupeptin (“lysis buffer”), and the crude lysates were centrifugedbriefly to remove insoluble material. Supernatants were incubated with3E8, a monoclonal antibody specific for ErbB2 (Fendly et al., CancerRes., 50:1550-1558 (1990)), covalently coupled to an insoluble support(Affi Prep-10™, Bio-Rad). The incubation was carried out overnight at 4°C. The immunoprecipitates were washed twice with ice cold lysis buffer,re-suspended in a minimal volume of SDS sample buffer, and run onSDS-PAGE. Western blots of the gels were then probed with a polyclonalanti-ErbB3 (Santa Cruz Biotech). The blots were scanned with areflectance scanning densitometer as described in Holmes et al.,Science, 256:1205-1210 (1992). After visualization with the ECLchemiluminescent substrate, the blots were stripped and re-probed with apolyclonal anti-ErbB2 (Santa Cruz Biotech). A duplicate plot probed withanti-ErbB2 showed that equal amounts of ErbB2 were immunoprecipitatedfrom each sample.

Results

A panel of monoclonal antibodies directed against the extracellulardomain of ErbB3 were evaluated for their ability to affect HRG bindingto ErbB3. The initial screen was carried out by incubating each of thepurified antibodies at a final concentration of 100 nM with 4E9H3 cellsin the presence of ¹²⁵I-HRG. 4E9H3 cells are ErbB3 transfectants of thehuman myeloid leukemia cell line K562. The K562 cell line does notexpress endogenous ErbB receptors or HRG. Therefore, heregulin bindingto 4E9H3 cells occurs exclusively through ErbB3. After incubating thesamples overnight on ice, cell associated counts were measured. As shownin FIG. 1, two of the anti-ErbB3 monoclonal antibodies (2F9 and 3E9)reduced the amount of ¹²⁵I-HRG bound to 4E9H3 cells relative to control(no antibody). However, several others significantly enhanced ligandbinding. These results suggested that these anti-ErbB3 antibodies wereable to increase the affinity for HRG binding and/or increase theavailability of HRG binding sites. To further characterize the influenceof these antibodies on HRG binding to ErbB3, dose-response experimentswere performed using the 3-8D6 antibody that increased HRG binding.4E9H3 cells were incubated with 100 pM of ¹²⁵I-HRG in the presence ofincreasing concentrations of the 3-8D6 antibody. Cell associated countswere then measured after an overnight incubation on ice. The results areshown in FIG. 2 as plots of cell associated counts versus antibodyconcentrations. There is a correlation between increased HRG binding andincreasing antibody concentration. Heregulin binding reached saturationbetween 10 and 100 nM IgG. The EC₅₀ value for the 3-8D6 antibody was 722pM. No decrease in the dose-response curves at high antibodyconcentrations were observed for either antibody.

Scatchard analysis of HRG binding was determined in the presence ofthese antibodies and the results are shown in Table 1. TABLE 1 Data SetK_(d) Sites/Cell Control 1.2 × 10⁻⁹ 3.6 × 10⁵ MAb 3-8D6 2.1 × 10⁻¹⁰ 2.4× 10⁵ FAb 3-8D6 2.8 × 10⁻¹⁰ 2.9 × 10⁵

In the absence of the antibody, a Kd of 1200 pM was measured for HRGbinding to ErbB3, which is in agreement with a previously measuredaffinity measurement of HRG binding to ErbB3. The number of bindingsites per cell was determined to be 36,000. In the presence of theantibody, 3-8D6, the measured binding constant for HRG binding issignificantly increased to 210 pM. However, the number of HRG bindingsites is not increased in the presence of 3-8D6.

To determine whether the increase in ErbB3 ligand binding affinity wasdependent on the antibody being divalent, HRG binding experiments wereperformed in the presence of 100 nM of a Fab fragment prepared by papaindigestion of the 3-8D6 antibody. Fab fragments used for theseexperiments were purified by Protein A affinity chromatography and bygel filtration chromatography. No intact IgG was detected in thispurified preparation by SDS-PAGE. As shown in FIG. 3, binding of HRG inthe presence of the intact antibody or the resulting Fab is nearlyidentical. Scatchard analysis of these data yield a dissociationconstant for HRG binding in the presence of Fab of 280 pM and the numberof receptors per cell determined from this experiment was alsoessentially the same as that of the control. These data are consistentwith those presented in FIG. 2, where the dose response curves with theintact antibodies showed a plateau rather than a bell-shaped curve athigher antibody concentration, where univalent antibody binding might beoccurring. Without being bound by any theory, these data suggest thatthe alteration in HRG binding observed in the presence of theseantibodies does not require a divalent antibody.

The effect of the 3-8D6 antibody in a receptor tyrosine phosphorylationassay, using the ovarian tumor cell line Caov3 which co-expresses ErbB2and ErbB3 was next examined. Cells were stimulated with 10 nM HRGfollowing a 60 minute pre-incubation with either the 3-8D6 antibody (at250 nM) or buffer (control). Whole cell lysates were analyzed on aWestern blot probed with anti-phosphotyrosine. HRG treatment did notstimulate phosphorylation in 4E9H3 cells. Treatment of 4E9H3 cells withthe 3-8D6 antibody did not induce phosphorylation of ErbB3 by itself nordid it have any effect on tyrosine phosphorylation in Caov3 cells. Amarked tyrosine phosphorylation signal was detected on a protein with amolecular size ˜180 kDa following HRG stimulation. Treatment of Caov3cells with 2C4, an antibody specific for ErbB2, was able to block theHRG-mediated tyrosine phosphorylation signal. When cells were treatedwith the anti-ErbB3 antibody, 3-8D6, prior to HRG stimulation, tyrosinephosphorylation was also decreased. By scanning densitometry of theanti-phosphotyrosine blots of whole cell lysates, it was observed that3-8D6 inhibits the phosphotyrosine signal at 180-185 kDa by about 80%(range 76-84%). This signal is contributed by tyrosine phosphateresidues on both ErbB3 and ErbB2. Treatment of Caov3 cells with the Fabfragments prepared from the 3-8D6 antibody, also reduced the HRGstimulated phosphorylation of the 180 kDa band relative to control.However, the inhibitory activity of the Fab was slightly less potentthan the intact antibody.

The 3-8D6 antibody-mediated increase in receptor affinity on cells whichexpress ErbB3 alone is analogous to the increase in affinity associatedwith co-expression of ErbB2 with ErbB3. Moreover, this antibody blocksthe HRG stimulated ErbB2 kinase activity in cells which express bothreceptors. To determine whether the anti-ErbB3 antibody competesdirectly with ErbB2 for binding to ErbB3, a series ofco-immunoprecipitation experiments were performed using Caov3 cells.Cells were pre-incubated with either antibody, or buffer (control) andthen treated with 10 nM HRG for 10 minutes. Lysates of the cells werethen immunoprecipitated with a monoclonal antibody against ErbB2.Immunoprecipitates were then analyzed by Western blot for the presenceof ErbB3. The results of these experiments indicated that ErbB3 waspresent in the ErbB2 immunoprecipitate of the HRG stimulated celllysate, but not in the immunoprecipitate of unstimulated lysate. Thesedata suggests that HRG drives the formation of an ErbB2-ErbB3 complex inCaov3 cells. ErbB3 was not detectable in the immunoprecipitate of thesample treated with the anti-ErbB2 monoclonal antibody, 2C4. Asignificant diminution in the ErbB3 signal was observed when the cellswere pre-incubated with the 3-8D6 antibody or its resulting Fab prior toHRG stimulation. These data indicate that the 3-8D6 antibody inhibitsthe formation of a ErbB2-ErbB3 complex following HRG treatment. Scanningdensitometry of the anti-ErbB3 Western blots of anti-ErbB2immunoprecipitates revealed that the anti-ErbB3 signal (which indicatesthe number of ErbB2-ErbB3 complexes present) is also diminished by 3-8D6by about 80% (range 71-90%). When duplicate blots were probed withanti-ErbB2, equivalent amounts of ErbB2 were present in all lanes.

1. An antibody which binds to ErbB3 protein and reducesheregulin-induced formation of an ErbB2-ErbB3 protein complex in a cellwhich expresses ErbB2 and ErbB3.
 2. The antibody of claim 1 whichfurther increases the binding affinity of heregulin for ErbB3 protein.3. The antibody of claim 1 which further reduces heregulin-induced ErbB2activation in the cell.
 4. The antibody of claim 1 which is a monoclonalantibody.
 5. The antibody of claim 1 which is humanized.
 6. The antibodyof claim 1 which is human.
 7. The antibody of claim 1 which is anantibody fragment.
 8. The antibody fragment of claim 8 which is a Fab.9. The antibody of claim 1 which is labelled.
 10. The antibody of claim1 which is immobilized on a solid phase.
 11. An antibody which binds toErbB3 protein and increases the binding affinity of heregulin for ErbB3protein.
 12. An antibody which binds to ErbB3 protein and reducesheregulin-induced ErbB2 activation in a cell which expresses ErbB2 andErbB3.
 13. An antibody which binds to ErbB3 protein and reducesheregulin binding thereto.
 14. The antibody of claim 13 which furtherreduces heregulin-induced ErbB2 activation in a cell which expressesErbB2 and ErbB3.
 15. The antibody of claim 1 which binds to the epitopebound by the 8B8 antibody.
 16. The antibody of claim 1 which has thecomplementarity determining regions of the 8B8 antibody.
 17. Acomposition comprising the antibody of claim 1 and a pharmaceuticallyacceptable carrier.
 18. A cell line which produces the antibody ofclaim
 1. 19. The cell line of claim 18 which is a hybridoma cell lineproducing the 8B8 antibody.
 20. A method for determining the presence ofErbB3 protein comprising exposing a cell suspected of containing theErbB3 protein to the antibody of claim 1 and determining binding of saidantibody to the cell.
 21. A kit comprising the antibody of claim 1 andinstructions for using the antibody to detect the ErbB3 protein.